JAMB Mathematics Past Questions & Answers - Page 387

1,931.

Find the remainder when 3x3 + 5x2 - 11x + 4 is divided by x + 3

A.

-4

B.

4

C.

1

D.

-1

Correct answer is C

x = -3
substitute x = -3 in 3x3 + 5x2 - 11x + 4
3(-3)3 + 5(-3)2 - 11(-3) + 4
-81 + 45 + 33 + 4
-81 + 82
= 1

1,932.

If the operation * on the set of integers is defined by P * Q = \(\sqrt{PQ}\), find the value of 4 * ( 8 * 32).

A.

8

B.

3

C.

16

D.

4

Correct answer is A

\(P\times Q=\sqrt{PQ}\\4\times(8\times32)=4\times\sqrt{8\times32}\\=4\times\sqrt{256}\\=4\times16\\=\sqrt{4\times16}\\=\sqrt{64}\\=8\)

1,933.

Given that the first and forth terms of G.P are 6 and 162 respectively, find the sum of the first three terms of the progression

A.

27

B.

8

C.

78

D.

48

Correct answer is C

\(a=6, U_4 = 162\\U_4 = ar^{4-1}\\U_4 = ar^3\\162 = 6(r)^3\\r^3 = 27\\r=\sqrt[3]{27}\\r=3\\S_4 = \frac{a(r^{n}-1)}{r-1}\\=\frac{6(3^{3}-1)}{3-1}\\=\frac{6(27-1)}{2}\\=3\times26\\=78\)

1,934.

What are the integer values of x which satisfy the inequality -1 < 3 -2x \(\leq\) 5?

A.

-1. 0, 1, 2

B.

-2, 1, 0 , -1

C.

0, 1, 2

D.

-1, 0, 1

Correct answer is D

-1 < 3 -2x and 3 - 2x \(\leq\) 5
2x < 3 + 1 and -2x \(\leq\) 5 - 3
2x < 4 and -2x \(\leq\) 2
x < 2 and x \(\geq\) 2/-2 = x \(\geq\) -1
If -1 \(\leq\) x < 2
it implies that x = -1, 0, 1

1,935.

y is inversely proportional to x and y = 4 when x = 1/2. Find x when y = 10.

A.

2.5

B.

10

C.

1/5

D.

1/10

Correct answer is C

y ∝ 1/x
y = K/x
K = xy
K = (1/2) * 4 ( when y = 4 and x = 1/2)
K = 2
∴y = 2/x
10 = 2/x (when y = 10)
10x = 2
x = 2/10
x = 1/5