Find the exact value of the definite integral, from x = 0 to x = 2, of 3x2 dx.
(Total for Question 8 is 1 mark)
9
Find the integral of 5e2x dx.
(Total for Question 9 is 1 mark)
10
Find the integral of 4/(x+2) dx, for x > -2.
(Total for Question 10 is 1 mark)
11
Using the substitution u = 3 + x2, find the integral of x √3+x2 dx.
(Total for Question 11 is 2 marks)
12
A curve satisfies dy/dx = 6x2/y, where y > 0, and passes through the point (0, 3). By separating the variables, find y in terms of x.
(Total for Question 12 is 2 marks)
13
Using the substitution u = sin(x), find the integral of sin2(x)cos(x) dx.
(Total for Question 13 is 2 marks)
14
Find the exact value of the definite integral, from x = 1 to x = e, of 1/x dx.
(Total for Question 14 is 2 marks)
15
f(x) = x e3x.
(a)Find the integral of f(x) dx, using integration by parts.(2)
(b)Hence find the exact value of the definite integral, from x = 0 to x = 1, of f(x) dx.(2)
(Total for Question 15 is 4 marks)
16
Find the integral of sin2(x)cos3(x) dx.
(Total for Question 16 is 3 marks)
17
The curve C has equation y = 1/√16-x2, for -4 < x < 4.
(a)Find the integral of 1/√16-x2 dx.(2)
(b)Hence show that the definite integral, from x = 0 to x = 2, of 1/√16-x2 dx, equals π/6.(2)
(Total for Question 17 is 4 marks)
18
f(x) = (5x - 7) / ((x-3)(x+1)).
(a)Express f(x) in the form A/(x-3) + B/(x+1), where A and B are constants to be found.(2)
(b)Hence find the integral of f(x) dx.(2)
(Total for Question 18 is 4 marks)
19
The curve C has equation y = 6x - x2. The line l has equation y = 2x. Find the area of the finite region bounded by C and l.
(Total for Question 19 is 3 marks)
20
The number of bacteria, N, in a culture is modelled by the differential equation dN/dt = N/50, where t is measured in hours. Initially there are 200 bacteria.
(a)By separating the variables, show that N = 200 et/50.(2)
(b)Find the time taken, in hours to 3 significant figures, for the population to reach 500.(2)
(Total for Question 20 is 4 marks)
Mark scheme · P15D Pure: Integration Depth: Fluency and Exam Drill
Question 1
B1 (x2+3)4 + c cao
Answer: (x2+3)4 + c
Question 2
B1 (1/3)e3x + c cao
Answer: (1/3)e3x + c
Question 3
B1 (1/2)ln(2x+1) + c cao
Answer: (1/2)ln(2x+1) + c
Question 4
B1 (1/4)sin(4x) + c cao
Answer: (1/4)sin(4x) + c
Question 5
B1 (2/3)(x3-1)3 + c cao
Answer: (2/3)(x3-1)3 + c
Question 6
B1 ln(x) + c cao
Answer: ln(x) + c
Question 7
B1 tan(x) + c cao
Answer: tan(x) + c
Question 8
B1 8 cao
Answer: 8
Question 9
B1 (5/2)e2x + c cao
Answer: (5/2)e2x + c
Question 10
B1 4ln(x+2) + c cao
Answer: 4ln(x+2) + c
Question 11
M1 substitutes u = 3+x2, du = 2x dx, to get integral of (1/2)√u du
A1 = (1/3)(3+x2)3/2 + c cao
Answer: (1/3)(3+x2)3/2 + c
Question 12
M1 separates variables and integrates: y2/2 = 2x3 + C
A1 uses (0,3) to find C = 4.5, giving y = √4x3+9
Answer: y = √4x3 + 9
Question 13
M1 substitutes u = sin(x), du = cos(x) dx, to get integral of u2 du
A1 = sin3(x)/3 + c cao
Answer: sin3(x)/3 + c
Question 14
M1 integrates to [ln x] between 1 and e
A1 = ln(e) - ln(1) = 1 cao
Answer: 1
Question 15
(a) M1 applies integration by parts with u=x, dv=e3xdx
(a) A1 (x/3)e3x - (1/9)e3x + c
(a) Answer: (x/3)e3x - (1/9)e3x + c
(b) M1 substitutes the limits x=0 and x=1 into the result of part (a)
(b) A1 (2e3 + 1)/9 cao (exact)
(b) Answer: (2e3 + 1)/9
Question 16
M1 rewrites cos3(x) = cos(x)(1-sin2(x)) and substitutes u = sin(x)
A1 integrates to u3/3 - u5/5
A1 = sin3(x)/3 - sin5(x)/5 + c cao
Answer: sin3(x)/3 - sin5(x)/5 + c
Question 17
(a) M1 uses the standard result for integral of 1/√a2-x2 dx with a=4
(a) A1 arcsin(x/4) + c cao
(a) Answer: arcsin(x/4) + c
(b) M1 substitutes the limits into the result of part (a): arcsin(0.5) - arcsin(0)
(b) A1 cso: = π/6, as required
(b) Answer: π/6
Question 18
(a) M1 sets up A(x+1) + B(x-3) = 5x-7 and compares coefficients (or substitutes x=3, x=-1)
(a) A1 A = 2, B = 3
(a) Answer: A = 2, B = 3
(b) M1 integrates each partial fraction term (ft from (a))
(b) A1 2ln(x-3) + 3ln(x+1) + c cao
(b) Answer: 2ln(x-3) + 3ln(x+1) + c
Question 19
M1 finds the intersections x=0 and x=4 by solving 6x-x2=2x
M1 sets up the integral of (4x-x2) dx between 0 and 4
A1 area = 32/3 cao
Answer: 32/3
Question 20
(a) M1 separates variables and integrates: ln N = t/50 + C
(a) A1 cso: uses N=200 at t=0 to obtain N = 200et/50
(a) Answer: N = 200et/50
(b) M1 sets 200et/50 = 500 and takes logarithms of both sides