Work with an online tutor on functions, graphs, logarithms and trigonometry in Concordia MATH 201. Start with a function or equation, even if you do not know how to begin. Your tutor can explain composition, inverse functions or domain restrictions and guide you through a related question.
Rational graphs without calculus: keep the missing inputs
Use factoring, signs and division to describe a rational graph. You do not need derivatives. A rational function is a quotient of polynomials, with every zero of its original denominator excluded. Cancelling a common factor simplifies the values at allowed inputs; it does not restore a missing input.
Factor and record exclusions from the original denominator.
Cancel common factors only where the original expression is defined. A cancelled factor gives a hole only when the remaining expression is finite there. A remaining denominator zero can still give a vertical asymptote.
For an x-intercept, solve for a zero output and check the input is allowed. For a y-intercept, evaluate at zero only if zero is in the domain.
Use polynomial division, or compare degrees, for end behaviour. A horizontal asymptote describes large positive and negative inputs; it is not a line the graph is forbidden to cross.
Check signs on either side of each vertical asymptote. Mark holes with open circles, asymptotes with dashed lines and actual intercepts with filled points. These features guide a sketch; they do not by themselves prove every turning point.
Worked example 1: one hole and one vertical asymptote
Describe f(x)=(x2−x−2)/(x2−4): domain, missing point, asymptotes and intercepts. Sketch the branches without differentiating.
First hint
Factor both quadratics. Keep both original exclusions before cancelling anything.
Follow the complete graph investigation
Factor: f(x)=(x−2)(x+2)(x−2)(x+1)=x+2x+1,x=−2,2. The domain is all real numbers except −2 and 2.
At x=2, the simplified expression is finite: 3/4. The original function is still undefined there, so mark a hole at (2,3/4), not a zero or a vertical asymptote.
At x=−2, the remaining denominator vanishes but the numerator is −1. There is a vertical asymptote x=−2. Writing f(x)=1−1/(x+2) shows that values grow without bound positively as x approaches −2 from the left, and negatively from the right.
The only x-intercept is (−1,0): the cancelled zero x=2 was excluded. Zero is allowed, giving y-intercept (0,1/2).
The remainder −1/(x+2) approaches zero for large ∣x∣, so the horizontal asymptote is y=1. The left branch lies above 1, and the right branch below 1, with an open circle at (2,3/4). The graph never equals 1 because −1/(x+2) is never zero.
Check a nearby value:f(3)=4/5, a point below the horizontal asymptote. A sketching tool might join across a tiny hole, so retain the algebraic domain even when the hole is hard to see.
Worked example 2: an oblique asymptote from division
Find the key graph features of g(x)=(x2+1)/(x−1). Explain the oblique (slant) asymptote without using derivatives.
First hint
Multiply (x−1)(x+1). What must be added to obtain x2+1?
Follow the division and graph checks
The only excluded input is x=1. Since x2+1>0 for every real input, there is no common factor and no hole.
Division gives g(x)=x+1+x−12. The difference g(x)−(x+1)=2/(x−1) approaches zero for large positive or negative x. Thus y=x+1 is the oblique asymptote. There is no horizontal asymptote. The difference never vanishes, so this particular graph never meets its oblique asymptote.
The vertical asymptote is x=1. Near 1 the numerator stays positive: approaching from the left gives large negative outputs, and from the right gives large positive outputs.
There is no real x-intercept because x2+1=0 has no real solution. The y-intercept is (0,−1).
For x<1, the remainder 2/(x−1) is negative, so the graph lies below its oblique asymptote; for x>1, it lies above. Useful checkpoints are g(−1)=−1 and g(2)=5.
Sketch honestly: show these verified features without claiming an exact location for a turning point. An asymptote is about the gap between the curve and a line, not about the output approaching a finite number when that line is oblique.
Four original problems: predict, sketch, then check
1. A repeated denominator factor
For p(x)=(x+1)/(x−2)2, state the domain, holes, intercepts and asymptotes. Do the two sides of the vertical asymptote go in opposite directions?
Hint 1
Close to 2, the numerator is positive and the squared denominator is positive on both sides.
Explained solution 1
The domain excludes 2. Nothing cancels, so there is no hole. The x-intercept is (−1,0), and the y-intercept is (0,1/4). The vertical asymptote is x=2; on both sides the outputs grow without bound positively. The numerator has smaller degree than the denominator, giving horizontal asymptote y=0. A repeated denominator factor does not force opposite-sided behaviour. The graph crosses its horizontal asymptote at (−1,0).
2. Cancellation does not restore the y-intercept
Investigate q(x)=x(x−3)/[x(x+2)]. Find the domain, hole, intercepts and asymptotes. Explain why substituting zero after cancellation would mislead you.
Hint 2
Record both denominator zeros first; then use (x−3)/(x+2) only on the original domain.
Explained solution 2
The domain excludes 0 and −2. Cancellation gives (x−3)/(x+2)=1−5/(x+2) on that domain. There is a hole at (0,−3/2), not a y-intercept. The x-intercept is (3,0), the vertical asymptote is x=−2, and the horizontal asymptote is y=1. At −2, outputs grow positively from the left and negatively from the right. The original denominator is zero at zero, so the original graph has no point on the y-axis.
3. Cross a horizontal asymptote
For u(x)=(x2+x)/(x2+1), find the domain, both types of axis intercept and any vertical or horizontal asymptote. Find where the graph crosses its horizontal asymptote.
Hint 3
The denominator is always positive. Write u(x)=1+(x−1)/(x2+1) and ask when the remainder is zero.
Explained solution 3
The domain is all real numbers; there are no holes or vertical asymptotes. Factoring the numerator gives x-intercepts (−1,0) and (0,0); the y-intercept is also (0,0). Equal leading coefficients give horizontal asymptote y=1. Solving u(x)=1 gives x=1, an allowed input, hence the crossing (1,1). Since x2+1>0, the remainder is negative for x<1 and positive for x>1: this really is a crossing, not merely a touch. End behaviour does not forbid a finite crossing.
4. Build a formula from graph features
Construct one rational function with vertical asymptote x=−2, horizontal asymptote y=2, x-intercept (3,0), and a hole at (1,−4/3). State its domain and y-intercept. Your task is to give a valid formula, not to prove that the features determine a unique function.
Hint 4
Start with 2(x−3)/(x+2), then introduce a common factor that excludes 1 without changing allowed outputs.
Explained solution 4
One answer is v(x)=(x+2)(x−1)2(x−3)(x−1),x=−2,1. The remaining denominator gives the vertical asymptote x=−2; the leading-coefficient ratio gives y=2. The allowed zero is 3. At the cancelled input 1, the simplified expression gives 2(1−3)/(1+2)=−4/3, the required missing point. Zero is allowed, and v(0)=−3, so the y-intercept is (0,−3). Writing only the simplified formula on its natural domain would wrongly fill the hole.
Choose your retry: if you restored an excluded input, repeat problem 2; if you confused a hole with unbounded behaviour, compare example 1 and problem 1; if you thought an asymptote was uncrossable, repeat problem 3. Bring your factored expression, domain and labelled sketch to a tutoring session. Tutoring is currently offered in English.
MATH 201 topics to review
Function notation and compositionGraph transformationsPolynomial and rational functionsExponential functionsLogarithmic functionsTrigonometric functions
Common difficulties
Tracking the domain through a composition
Distinguishing an inverse function from a reciprocal
MATH 201 review: early functions and later trigonometry
For weeks 1–6 preparation, start with the domain, inverse-function and logarithm checks, then the rational-graph workshop. Keep the fourth check for later trigonometry. Show your steps before opening the solutions.
The Fall 2026 outline places the midterm on weeks 1–6. Trigonometry begins in week 7, so the fourth check is later-course practice, not part of that early scope. Confirm your section’s current instructions. This selection is not a complete mock exam.
Before you start: Allow 25 minutes for a first attempt, then 15 minutes to check and retry any missed steps.
1. Combine two restrictions
Find the real domain of r(x)=x+2/(x−1). Decide separately whether x=−2 and x=1 are allowed.
Show the explained solution
The square root requires x+2≥0, hence x≥−2. The denominator requires x=1. Both conditions must hold at once.
The domain is [−2,1)∪(1,∞). The input −2 is allowed because the numerator is zero and the denominator is −3. The input 1 is excluded because division by zero is undefined.
If you excluded the square-root endpoint, distinguish a nonnegative square-root argument from the strictly positive argument required by a logarithm.
Let h(x)=2(x−3)2−5 for x≥3. Describe the transformations of y=x2, then find the inverse and its domain.
Show the explained solution
The graph moves three units right, stretches vertically by a factor of two, then moves five units down. The specified domain keeps the right-hand branch, where the function is one-to-one.
The range of h is [−5,∞). From t=2(x−3)2−5, use x−3≥0 to take the nonnegative square root:
h−1(t)=3+2t+5,t≥−5. Its range is [3,∞). The inverse’s domain comes from the original range.
At t=3, the inverse returns x=5, and h(5)=3. Keeping both square-root signs would fail to define the inverse of the selected branch.
Write one restriction per operation, intersect the restrictions, then check a boundary and an excluded value. Redo that question before starting another full set.
Inverse error in question 2
List domain and range side by side. Swap those sets for the inverse, then verify one composition and one numeric input.
Missing trigonometric solutions in question 4
Factor first, solve every factor, then filter by the interval. Practise one assigned equation with two different trigonometric branches.
For a lesson, you can bring any of these questions even if you have not started it. If you have attempted work or a current outline, include it. Your tutor can help you choose a starting point and work through functions, algebraic restrictions or trigonometry with you.
For a real input x, simplify x−4x2−16 and state which input value must remain excluded from its domain.
Show the reasoning
The denominator is zero at x=4, so first require x=4. Factor the difference of squares: x2−16=(x−4)(x+4). For the allowed inputs only, divide numerator and denominator by the nonzero factor x−4. The result is x+4, still with x=4.
Composition order changes the function and its domain
The same two formulas can produce different composite functions. This example follows the input through each operation, then uses the range to determine an inverse function’s domain.
1. Apply the inner function first
Let x be a real input. We use the nonnegative real square root. The notation f∘g means apply g first, then apply f to that output; name this composite function h. Let f(x)=x−1 and g(x)=3x+2. Then h(x)=(f∘g)(x)=3x+1. The square root requires 3x+1≥0, so h has domain (allowed inputs) [−31,∞) and range (possible outputs) [0,∞). The input to f is g(x), not the original x.
2. Reverse the order and check again
The reverse composition is k(x)=(g∘f)(x)=3x−1+2. Here the square root happens first, so the domain is [1,∞). Its range is [2,∞). Thus f∘g and g∘f differ in both formula and allowable inputs.
3. Find the inverse with its input restriction
An inverse reverses input and output. The function h is strictly increasing on its domain, so each value in its range comes from exactly one input. Write y for the output of h; after solving for the original input, use t to name an input to the inverse. For h, start from y=3x+1, where y≥0. Solving gives x=(y2−1)/3. Therefore h−1(t)=3t2−1,t≥0. The inverse’s domain is the original function’s range; its range is [−31,∞).
4. Check what squaring can hide
Composing back gives h(h−1(t))=t2=∣t∣. This equals t on the required domain t≥0. If you incorrectly allow t=−2, the expression returns 2, not −2. The restriction is essential, even though the inverse formula’s polynomial expression can be evaluated at negative numbers.
Try it yourself
Find k−1 for k(x)=3x−1+2. State its domain and range, and explain the restriction.
Show the explained solution
From t=3x−1+2, obtain k−1(t)=1+(3t−2)2,t≥2. Its range is [1,∞). The input restriction t≥2 comes from the range of k; it also makes (t−2)/3 nonnegative before squaring.
For a new composition or inverse, write the formula, domain and range together. Test one boundary input and one excluded input to see whether the restrictions make sense.
How tutoring can help
You can bring a function or equation even if you do not know where to start. Your tutor can help you identify the allowed inputs, sketch the graph and work through a transformation or composition. For logarithms and inverse functions, you can work through the inverse operations together before trying another equation.
Exam preparation for MATH 201
For each function family, practise formula, domain, sketch and transformation. Mix logarithmic and trigonometric equations so you must choose the method.
Use your section’s outline to choose the chapters to review. We work through permitted practice and comparable problems, without completing graded assignments or exams on your behalf.
Working with triangle lengths and angles?
Start by checking whether a right angle is given. For a right triangle, review choosing sine, cosine or tangent. For a triangle without a right angle, use the sine and cosine laws: match opposite sides and angles, choose a method from the given data, and check whether two different triangles are possible.
These are later-course topics in the Fall 2026 outlines. Use your section’s announced exam scope to decide when to practise them. After the lesson, try a new question without its solution and explain why your chosen method applies.
Related courses
Useful links for preparation or further study—not transfer equivalencies or a required registration sequence.
Learn why cancelling a factor preserves an excluded input and distinguish a function value from a limit, with a worked example and three self-checks for Concordia MATH 203 and McGill MATH 140.
Build exponential models from constant ratios, derive logarithm laws, connect inverse graphs and solve equations with domain checks and growth/decay thresholds. Six worked examples, four diagrams and twelve explained practice questions.
Connect inputs, tables and graphs; transform functions, check composition domains, reverse restricted rules and choose piecewise branches. Eight numbered worked examples, five diagrams and twenty explained practice questions.
Connect radians, signed coordinates and trigonometric graphs. Twelve worked examples and twenty-three questions, including sinusoidal models, threshold intervals, identities and quadratic equations.
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