Pure Mathematics — Paper 1 · AQA AS Mathematics (sample) · Drill 3 of 3
Why this topic matters. Integration is examined on every AQA AS Mathematics (sample) Paper 1 and Paper 2, typically carrying 10–18 marks per sitting. Indefinite integration (finding the general function) and definite integration (computing exact areas) both appear consistently. Area under a curve — including areas trapped between two curves — is examined in roughly 4 of every 5 sittings.
The scaffold to use (RICE Framework)
Raise the power by 1: ∫x^n dx ⇒ xn+1/(n+1) + C.
Include the +C for every indefinite integral — never omit it.
Compute limits for definite integrals: [F(x)]ᵃᵇ = F(b) − F(a).
Ensure negative area is handled correctly: area between curve and axis = |∫|; subtract where curve is below axis.
Foundational — recall and single-step application
Q1. Find ∫(3x² + 4x − 2) dx.
Foundational
[2 marks]
Method to use
Consider Power Rule Integration — integrate each term separately using ∫x^n dx = xn+1/(n+1); add +C.
M1
Integrate term by term: ∫3x²dx = x³; ∫4x dx = 2x²; ∫(−2) dx = −2x.
AO1 — applying power rule integrationCommon mistake: Forgetting to add +C for an indefinite integral.
A1
∫(3x² + 4x − 2) dx = x³ + 2x² − 2x + C.
AO1 — correct integral with +C
M1
F(x) = x³/3 + x. (No +C needed for definite integrals.)
AO1 — indefinite integral for definite evaluationCommon mistake: Carrying +C through into the definite evaluation.
Mid-tier — application and analysis (exam-bulk questions)
Q7. Find the area enclosed between the curve y = x² − 4 and the x-axis.
Mid-tier
[5 marks]
Method to use
Consider Area with Axis/Between Curves — find where y = 0 to get the limits; the curve dips below the x-axis so use |∫|.
M1
Set y = 0: x² = 4 ⇒ x = ±2. Limits: x = −2 to x = 2.
AO1 — finding x-intercepts
M1
∫−22(x² − 4) dx. F(x) = x³/3 − 4x.
AO1 — setting up the integral
A1
F(2) = 8/3 − 8 = −16/3. F(−2) = −8/3 + 8 = 16/3. Integral = −16/3 − 16/3 = −32/3.
AO1 — evaluating the definite integral
A1
Area = |−32/3| = 32/3 square units.
AO2 — taking absolute value for area below x-axisCommon mistake: Giving −32/3 as the area. Area is always positive; take |integral|.
A1
By symmetry about y-axis: Area = 2|∫₀²(x²−4)dx| = 2|(8/3−8)| = 2⋅16/3 = 32/3. ✓
AO2 — symmetry check
Q8. Find the area enclosed between y = 6x − x² and y = x².
Mid-tier
[6 marks]
Method to use
Consider Area with Axis/Between Curves — set the two equations equal to find intersection x-values; then integrate (top − bottom) between them.
M1
Set equal: 6x − x² = x² ⇒ 6x = 2x² ⇒ x(x−3) = 0. x = 0 or x = 3.
AO1 — finding intersection pointsCommon mistake: Forgetting to find both intersection points, or using the wrong limits.
M1
Top curve: 6x−x² ≥ x² on [0,3] (check at x=1: 5 ≥ 1 ✓). Integrate (top−bottom): ∫₀³(6x−2x²) dx.
AO2 — identifying top and bottom curves
A1
Area = 9 − 0 = 9 square units.
AO1 — correct area
A1
Check: the parabola y=x² is below y=6x−x² for 0<x<3 (positive enclosed area). ✓
AO2 — sign verification
A1
Alternatively integrate each curve separately and subtract: more work; the (top−bottom) method is faster.
AO2 — noting the efficient method
Q9. Given that ∫₀ᴷ(4x + 1) dx = 12, find the value of k.
Mid-tier
[5 marks]
Method to use
Consider Definite Integration (Limits) — evaluate the definite integral in terms of k, set equal to 12, and solve.
M1
F(x) = 2x² + x. ∫₀ᴷ(4x+1)dx = [2x²+x]₀ᴷ = 2k² + k − 0 = 2k² + k.
AO1 — setting up the integral in terms of k
M1
Set equal to 12: 2k² + k − 12 = 0.
AO1 — forming the equation
A1
Solve the quadratic 2k² + k − 12 = 0. It does not factorise over the integers (discriminant 1² + 4·2·12 = 97 is not a perfect square), so use the quadratic formula: k = (−1 ± √97) / 4.
AO1 — solving for k
A1
Since k is an upper limit of integration we take the positive root: k = (−1 + √97) / 4 ≈ 2.21 (3 s.f.).
AO1 — exact answer
A1
y = x(4−x) ≥ 0 for 0 ≤ x ≤ 4, so the curve is above the x-axis throughout. Area = integral directly.
AO2 — justifying no sign correction needed
Q12. Find ∫(x1/3 + x−3) dx.
Mid-tier
[4 marks]
Method to use
Consider Power Rule Integration — apply ∫x^n dx = xn+1/(n+1) + C to each term separately.
M1
∫x1/3 dx = x4/3/(4/3) = (3/4)x4/3. ∫x−3 dx = x−2/(−2) = −(1/2)x−2.
AO1 — applying power rule to fractional and negative exponentsCommon mistake: Increasing the exponent without dividing by the new exponent.
A1
∫(x1/3 + x−3) dx = (3/4)x4/3 − (1/2)x−2 + C.
AO1 — correct result with +C
A1
Equivalently: (3/4)∛(x⁴) − 1/(2x²) + C.
AO2 — writing in alternative notations
A1
[−4/x]₁² = (−4/2) − (−4/1) = −2 + 4 = 2.
AO1 — applying limits correctlyCommon mistake: Sign error in [−4/x]: −4/2 = −2, not +2; and −4/1 = −4, not +4.
A1
Area of R = 2 square units.
AO1 — correct area
A1
4/x² > 0 for all x ≠ 0, so no sign-correction needed. ✓
AO2 — confirming sign
Q14. Find the x-coordinates of points where y = x³ − 3x intersects y = 2. Hence find the area enclosed between y = x³ − 3x and y = 2 that lies entirely above y = 2.
Mid-tier
[6 marks]
Method to use
Consider Area with Axis/Between Curves — set curves equal to find limits; integrate (top − bottom = y − (x³−3x)) between those limits.
M1
Area = ∫₀ᶀ sin(x) dx = [−cos(x)]₀ᶀ.
AO1 — setting up the definite integral of sin(x)
A1
= (−cos π) − (−cos 0) = (−(−1)) − (−1) = 1 + 1 = 2. ✓
AO1 — correct evaluationCommon mistake: cos π = −1 and cos 0 = 1; sign errors here are extremely common.
A1
sin(x) ≥ 0 on [0, π], so the integral gives area directly (no modulus needed).
AO2 — justifying sign
A1
This classic result (area = 2) is worth memorising for efficiency.
AO2 — highlighting the key result
Q16. The curve C has equation y = x² + 2x − 3. (a) Find where C crosses the x-axis. (b) Find the area between C and the x-axis.
Mid-tier
[6 marks]
Method to use
Consider Area with Axis/Between Curves — for (b), integrate between the x-intercepts found in (a); the parabola opens upward so it dips below the axis between intercepts.
M1
(a) x² + 2x − 3 = 0 ⇒ (x+3)(x−1) = 0 ⇒ x = −3 or x = 1.
AO1 — finding x-intercepts by factorising
A1
C crosses x-axis at x = −3 and x = 1.
AO1 — correct x-values
M1
(b) Between x = −3 and x = 1, the curve is below the x-axis (check at x=0: y=−3 < 0). Area = |∫−31(x²+2x−3) dx|.
AO2 — identifying sign for area calculation
M1
At x=1/4: √(1/4)=1/2 and (1/4)²=1/16. So √x > x² on (0,1). Integrate (√x−x²) from 0 to 1.
AO2 — identifying the top curve
M1
∫₀₁(x1/2 − x²) dx = [(2/3)x3/2 − x³/3]₀₁.
AO1 — setting up the integral
A1
At x=1: 2/3 − 1/3 = 1/3. At x=0: 0.
AO1 — evaluating the integral
A1
Enclosed area = 1/3 square units.
AO1 — correct areaCommon mistake: Using wrong limits or integrating (x²−√x) giving −1/3; area must be positive.
A1
Note: by symmetry y=x² and y=√x are reflections of each other in y=x; the enclosed area must be symmetric too.
AO2 — elegance check
Q19. A function f has f′(x) = 3x² − 12x + 9. The curve y = f(x) has a local maximum at x = 1 with f(1) = 8. Find f(x) and the area between y = f(x) and the line y = f(3) for 1 ≤ x ≤ 3.
Stretch
[8 marks]
Method to use
Consider Power Rule Integration — integrate f′ and use f(1)=8 to find the constant; then find f(3); integrate (f(x)−f(3)) from 1 to 3.
M1
f(x) = x³ − 6x² + 9x + C. f(1) = 1−6+9+C = 4+C = 8 ⇒ C = 4.
AO1 — integrating and finding C
A1
f(x) = x³ − 6x² + 9x + 4.
AO1 — correct f(x)
M1
f(3) = 27−54+27+4 = 4. Line y = 4. Area = ∫₁³(f(x) − 4) dx = ∫₁³(x³−6x²+9x) dx.
AO2 — setting up the area integral
A1
Area = 27/4 − 11/4 = 16/4 = 4 square units.
AO1 — correct final area
A1
The local max is at x=1 (f′(1)=3−12+9=0 ✓) and f(1)=8 > f(3)=4, so the curve is above y=4 on (1,3). Area is positive. ✓
AO2 — sign and logic verification
A1
Local minimum at x=3: f′(3)=27−36+9=0 ✓. The curve touches y=4 again at the minimum, making the bounded area well-defined.
AO2 — confirming the geometry
Q20. The region R is bounded above by y = 4x − x² and below by y = x. (a) Find the area of R. (b) Find the x-coordinate of the vertical line that divides R into two equal areas.
Stretch
[9 marks]
Method to use
Consider Area with Axis/Between Curves — for (a) integrate (top−bottom) between intersections; for (b) set ∫ᵃ = half the total area and solve for p.