JAMB Mathematics Past Questions & Answers - Page 104

516.

Solve x2 − 2x − 3 = 0

A.

x = 2 or 1

B.

x = 3 or -1

C.

x = 1 or 0

D.

x = 1 or 2

Correct answer is B

x2 − 2x − 3 = 0

−3x + x = − 2x

− 3x × x = − 3x2

(x2 − 3x)(x − 3) = 0

(x − 3)(x + 1) = 0

Either (x − 3) = 0 or (x + 1) = 0

x = 3 or − 1

517.

Find the value of x if \( [ 1 ÷ 64^{(x + 2)}]= [4^{(x − 3)} ÷ 16^x ] \)

A.

\( \frac{3}{2} \)

B.

\( \frac{2}{3} \)

C.

\( \frac{1}{3} \)

D.

\( -\frac{3}{2} \)

Correct answer is D

\( [ 1 ÷ 64^{(x + 2)}]= [4^{(x − 3)} ÷ 16^x ] \)

\( 64^{−(x + 2)} = [4^{(x − 3)}] ÷[16^x] \)

breakdown 4,16,64 into a small index no

\( 2^{−6(x + 2)} = 2^{2(x − 3)} ÷ 2^{4(x)} \)

\( 2^{−6x− 12} = 2^{2x − 4x − 6} \)

\( 2^{−6x −12} = 2^{−2x − 6} \)

− 6x − 12 = − 2x − 6

Collect the like term

−6x + 2x = −6 + 12

−4x =6

x = \( \frac{6}{4} \)

x = \( \frac{−3}{2} \)

518.

A man sells his new brand car for N420,000 at a gain of 15%. What did it cost him?

A.

N410,000

B.

N365, 217

C.

N157, 250

D.

N257,000

Correct answer is B

Cost Price:

Selling price = 100 : (100 + 15)

= 100 : 115

Cost Price

= 100 ÷ 115 of selling price (i.e N420,000)

= 100 ÷ 115 × N420,000

= N365,217.4

∴ Cost Price = N365, 217

519.

Find x if 132x = 70 eight.

A.

5

B.

3

C.

6

D.

1

Correct answer is C

132x = 708

\( 1 × x^2 + 3 × x^1 + 2 × x^0 \)

\( 7 × 8^1 + 0 × 8^0 \)

\( x^2 + 3x + 2 − 56 = 0 \)

\( x^2 + 3x − 54 = 0 \)

x(x + 9)−6(x + 9) = 0

(x + 9)(x − 6) = 0

Either (x + 9) = 0 or (x − 6) = 0

x = − 9 or +6

The positive values for x = 6

The base number for 132x = 1326

520.

Given that A = {3, 4, 1, 10, ⅓ }

B = {4, 3,⅓, ⅓, 7}.

Find A∩B

A.

{}

B.

{⅓, 1, 2}

C.

{3, 4, ⅓}

D.

{1, 3, ⅓}

Correct answer is C

A ∩ B = {3, 4, ⅓}