JAMB Mathematics Past Questions & Answers - Page 405

2,021.

Evaluate \(\int \sin 3x \mathrm d x\)

A.

(2/3) cos 3x + c

B.

(1/3) cos 3x + c

C.

(-1/3) cos 3x + c

D.

(-2/3) cos 3x + c

Correct answer is C

\(\int \sin 3x \mathrm d x = - \frac{\cos 3x}{3} + c\)

= \(-\frac{1}{3} (\cos 3x) + c\)

2,022.

The slope of the tangent to the curve y = 3x\(^2\) - 2x + 5 at the point (1, 6) is

A.

4

B.

1

C.

6

D.

5

Correct answer is A

y = 3x\(^2\) - 2x + 5

Slope = \(\frac{\mathrm d y}{\mathrm d x} = 6x - 2\)

At x = 1,

Slope : 6(1) - 2 = 4.

2,023.

Find the derivative of \(y = \sin^{2} (5x)\) with respect to x.

A.

10 sin 5x cos 5x

B.

5 sin5x cos 5x

C.

2 sin 5x cos 5x

D.

15 sin 5x cos 5x

Correct answer is A

\(y = \sin^{2} (5x)\)

Let u = sin 5x

\(\frac{\mathrm d u}{\mathrm d x} = 5 \cos 5x\)

\(\therefore y = u^{2}\)

\(\frac{\mathrm d y}{\mathrm d u} = 2u\)

\(\frac{\mathrm d y}{\mathrm d x} = 2u . 5 \cos 5x\)

= \(10u \cos 5x\)

= \(10 \sin 5x \cos 5x\)

2,024.

If dy/dx = 2x - 3 and y = 3 when x = 0, find y in terms of x.

A.

2x2 - 3x

B.

x2 - 3x

C.

x2 - 3x - 3

D.

x2 - 3x + 3

Correct answer is D

dy/dx = 2x - 3
y = ∫2x - 3 dx => y = x2 - 3x + c
3 = (0)2 - 3(0) + c
=> c = 3

Thus y = x2 - 3x + 3

2,025.

A trader bought goats for N4000 each. He sold them for N180,000 at a loss of 25%. How many goats did he buy?

A.

60

B.

50

C.

45

D.

36

Correct answer is A

Let the number of goats be X
C.P of X goats = N4000X
S.P of X goats = (75/100) x 4000X = N3000X

3000X = 180,000

=> X = 180000/3000 = 60.
X = 60 goats