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29. Evaluate: [tex] \int_1^3 x^2(4x + 3) \, dx [/tex].
- A. 106
- B. 110
- C. 2182
- D. 2192
[WASSCE June 2011 Qu 10]

30. Evaluate: [tex] \int_4^9 \frac{dx}{\sqrt{x}} [/tex].
- A. 1
- B. 2
- C. 3
- D. 4
[WASSCE Nov 2011 Qu 23]

31. If [tex] \int_{-2}^3 (ct - 1) \, dt = 0 [/tex], find the value of [tex] c [/tex].
- A. -2
- B. [tex] -\frac{2}{5} [/tex]
- C. [tex] \frac{2}{5} [/tex]
- D. 2
[WASSCE Nov 2011 Qu 34]

32. Evaluate [tex] \int_{-1}^1 (x^3 - x) \, dx [/tex].
- A. -1
- B. [tex] -\frac{1}{2} [/tex]
- C. 0
- D. [tex] \frac{1}{2} [/tex]
[WASSCE June 2012 Qu 38]

Evaluate [tex] \int_1^2 (4x^3 - 6x^2 + 1) \, dx [/tex].
- A. 2
- B. 3
- C. 4
- D. 5
[WASSCE Nov 2012 Qu 7]


Sagot :

Alright, let's evaluate each of the integrals step-by-step.

### Question 29

Evaluate: [tex]\(\int_1^3 x^2(4x + 3) \, dx\)[/tex].

First, simplify the integrand:

[tex]\[ x^2(4x + 3) = 4x^3 + 3x^2 \][/tex]

Now, find the antiderivative:

[tex]\[ \int (4x^3 + 3x^2) \, dx = \int 4x^3 \, dx + \int 3x^2 \, dx \][/tex]

[tex]\[ = 4 \int x^3 \, dx + 3 \int x^2 \, dx \][/tex]

[tex]\[ = 4 \left(\frac{x^4}{4}\right) + 3 \left(\frac{x^3}{3}\right) \][/tex]

[tex]\[ = x^4 + x^3 \][/tex]

Now evaluate it from [tex]\(x = 1\)[/tex] to [tex]\(x = 3\)[/tex]:

[tex]\[ \left[ x^4 + x^3 \right]_1^3 = (3^4 + 3^3) - (1^4 + 1^3) \][/tex]

[tex]\[ = (81 + 27) - (1 + 1) \][/tex]

[tex]\[ = 108 - 2 \][/tex]

[tex]\[ = 106 \][/tex]

Thus, the answer is A. [tex]\(106\)[/tex].

### Question 30

Evaluate: [tex]\(\int_4^9 \frac{dx}{\sqrt{x}}\)[/tex].

Rewrite the integrand:

[tex]\[ \frac{1}{\sqrt{x}} = x^{-1/2} \][/tex]

Now, find the antiderivative:

[tex]\[ \int x^{-1/2} \, dx = \int x^{-\frac{1}{2}} \, dx \][/tex]

Applying the power rule:

[tex]\[ \int x^{-\frac{1}{2}} \, dx = \frac{x^{-\frac{1}{2} + 1}}{-\frac{1}{2} + 1} = \frac{x^{\frac{1}{2}}}{\frac{1}{2}} = 2x^{\frac{1}{2}} \][/tex]

[tex]\[ = 2\sqrt{x} \][/tex]

Now evaluate it from [tex]\(x = 4\)[/tex] to [tex]\(x = 9\)[/tex]:

[tex]\[ \left[ 2\sqrt{x} \right]_4^9 = 2\sqrt{9} - 2\sqrt{4} \][/tex]

[tex]\[ = 2(3) - 2(2) \][/tex]

[tex]\[ = 6 - 4 \][/tex]

[tex]\[ = 2 \][/tex]

Thus, the answer is B. [tex]\(2\)[/tex].

### Question 31

Given: [tex]\(\int_{-2}^3 (ct - 1) \, dt = 0\)[/tex]. Find the value of [tex]\(c\)[/tex].

First, find the antiderivative:

[tex]\[ \int (ct - 1) \, dt = c \int t \, dt - \int 1 \, dt \][/tex]

[tex]\[ = c \left(\frac{t^2}{2}\right) - t \][/tex]

[tex]\[ = \frac{ct^2}{2} - t \][/tex]

Now, evaluate it from [tex]\(t = -2\)[/tex] to [tex]\(t = 3\)[/tex]:

[tex]\[ \left[ \frac{ct^2}{2} - t \right]_{-2}^3 = \left(\frac{c(3)^2}{2} - 3\right) - \left(\frac{c(-2)^2}{2} + 2\right) \][/tex]

[tex]\[ = \left(\frac{9c}{2} - 3\right) - \left(\frac{4c}{2} + 2\right) \][/tex]

[tex]\[ = \frac{9c}{2} - 3 - 2c - 2 \][/tex]

[tex]\[ = \frac{9c}{2} - \frac{4c}{2} - 5 \][/tex]

[tex]\[ = \frac{5c}{2} - 5 \][/tex]

Set it equal to 0:

[tex]\[ \frac{5c}{2} - 5 = 0 \][/tex]

[tex]\[ \frac{5c}{2} = 5 \][/tex]

[tex]\[ 5c = 10 \][/tex]

[tex]\[ c = 2 \][/tex]

Thus, the answer is D. [tex]\(2\)[/tex].

### Question 32

Evaluate: [tex]\(\int_{-1}^1 (x^3 - x) \, dx\)[/tex].

First, find the antiderivative:

[tex]\[ \int (x^3 - x) \, dx = \int x^3 \, dx - \int x \, dx \][/tex]

[tex]\[ = \left(\frac{x^4}{4}\right) - \left(\frac{x^2}{2}\right) \][/tex]

[tex]\[ = \frac{x^4}{4} - \frac{x^2}{2} \][/tex]

Now evaluate it from [tex]\(x = -1\)[/tex] to [tex]\(x = 1\)[/tex]:

[tex]\[ \left[ \frac{x^4}{4} - \frac{x^2}{2} \right]_{-1}^1 = \left(\frac{(1)^4}{4} - \frac{(1)^2}{2}\right) - \left(\frac{(-1)^4}{4} - \frac{(-1)^2}{2}\right) \][/tex]

[tex]\[ = \left(\frac{1}{4} - \frac{1}{2}\right) - \left(\frac{1}{4} - \frac{1}{2}\right) \][/tex]

[tex]\[ = \left(\frac{1}{4} - \frac{2}{4}\right) - \left(\frac{1}{4} - \frac{2}{4}\right) \][/tex]

[tex]\[ = \left(\frac{-1}{4}\right) - \left(\frac{-1}{4}\right) \][/tex]

[tex]\[ = -\frac{1}{4} + \frac{1}{4} \][/tex]

[tex]\[ = 0 \][/tex]

Thus, the answer is C. [tex]\(0\)[/tex].

### Question 33

Evaluate: [tex]\(\int_1^2 (4x^3 - 6x^2 + 1) \, dx\)[/tex].

First, find the antiderivative:

[tex]\[ \int (4x^3 - 6x^2 + 1) \, dx = 4 \int x^3 \, dx - 6 \int x^2 \, dx + \int 1 \, dx \][/tex]

[tex]\[ = 4 \left(\frac{x^4}{4}\right) - 6 \left(\frac{x^3}{3}\right) + x \][/tex]

[tex]\[ = x^4 - 2x^3 + x \][/tex]

Now evaluate it from [tex]\(x = 1\)[/tex] to [tex]\(x = 2\)[/tex]:

[tex]\[ \left[ x^4 - 2x^3 + x \right]_1^2 = (2^4 - 2(2^3) + 2) - (1^4 - 2(1^3) + 1) \][/tex]

[tex]\[ = (16 - 16 + 2) - (1 - 2 + 1) \][/tex]

[tex]\[ = (2) - (0) \][/tex]

[tex]\[ = 2 \][/tex]

Thus, the answer is A. [tex]\(2\)[/tex].
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