Algebra and functions practice problems A level Maths, Topic 1
Indices and surds, quadratics and the discriminant, the factor theorem, composite and inverse functions, and partial fractions. Try each question before you look: use the hint if you are stuck, then reveal the worked solution one step at a time.
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Key equations for algebra and functions
| b2 − 4ac | discriminant: > 0 two roots, = 0 one, < 0 none |
|---|---|
| f(a) = 0 ⇒ (x − a) is a factor | factor theorem |
| fg(x) = f(g(x)) | composite function |
| am/n = (n√a)m | fractional indices |
A formula booklet is provided in the exam. Answers within 2.5% are marked correct, and you can type fractions such as 1/6. What the booklet gives you, and what it leaves out, is in our A level Maths formula booklet guide.
Warm-up questions
Quick checks on the core ideas. If these feel easy, go straight to the exam-style questions.
Hint
b2 − 4ac with a = 2, b = −3, c = 5.
Worked solution
- (−3)2 − 4(2)(5) = 9 − 40.
- = −31, so there are no real roots.
Hint
Take the cube root first, then square.
Worked solution
- ∛8 = 2.
- 22 = 4.
Hint
Use the factor theorem: test f(a) for each.
Worked solution
- f(1) = 1 − 2 − 5 + 6 = 0.
- So (x − 1) is a factor: B. (f(−1) = 8, f(2) = −4, f(−3) = −24.)
Exam-style questions
Questions at the level of the A level Maths exam. The ones marked Challenge combine more than one idea.
Hint
Multiply top and bottom by (3 + √3).
Worked solution
- 6(3 + √3)/((3 − √3)(3 + √3)) = 6(3 + √3)/6.
- = 3 + √3, so a = 3.
Hint
Equal roots: the discriminant is zero.
Worked solution
- k2 − 36 = 0.
- k = 6 (taking k > 0).
Hint
Apply g first, then f.
Worked solution
- g(3) = 9.
- f(9) = 2(9) + 1 = 19.
Hint
Find the inverse, or solve f(x) = 5.
Worked solution
- (x + 4)/3 = 5 gives x + 4 = 15.
- f−1(5) = 11.
Hint
Multiply through, then substitute x = 1.
Worked solution
- 5x + 1 = A(x − 1) + B(x + 1).
- x = 1: 6 = 2B.
- B = 3 (and A = 2, from x = −1).
Exam question practice
One original exam-style question in the style of an A level paper. Answer it in full, with working, before you open the mark scheme: M marks are for method, A marks for accurate answers that follow from it, and B marks for correct statements on their own.
Exam-style question style · 6 points · about 8 minutes
f(x) = x3 − 7x − 6.
- (a) Use the factor theorem to show that (x + 1) is a factor of f(x).
- (b) Factorise f(x) completely.
- (c) Hence solve f(x) = 0.
Write your full answer on paper first, then open the scoring guide and tick each point you earned.
Scoring guide and model answer
Part (a)
f(−1) = −1 + 7 − 6 = 0, so (x + 1) is a factor.
Part (b)
f(x) = (x + 1)(x2 − x − 6) = (x + 1)(x + 2)(x − 3).
Part (c)
x = −1, x = −2 or x = 3.
Your mark: 0 of 6
Common mistakes in algebra and functions
- Getting the sign wrong in the factor theorem: f(−1) = 0 means (x + 1) is a factor.
- Applying a composite function in the wrong order: fg(x) means g first.
- Forgetting to multiply the numerator as well when rationalising.
- Dividing by a variable that could be zero when solving.
Keep going
Revise the ideas behind these questions:
Then try real exam questions: A level Maths past papers, with official scoring guidelines. · All A level Maths units