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JAMB Mathematics Past Questions & Answers - Page 18

86.

Factorize 4a2 - 9b2

A.

(2a-3b) (2a+3b)

B.

(2a-b) (2a+3b)

C.

(2a-3b) (a+3b)

D.

(a-3b) (a+3b)

Correct answer is A

Check:
(2a-3b) (2a+3b)

4a2 + 6ab - 6ab - 9b2

 4a2 - 9b2

87.

Find x if the mean of 2x, 4x, 2x - 13 and 6x is 4.

A.

1.5

B.

2.0

C.

1.0

D.

0.5

Correct answer is B

mean (4) =  2x+4x+2x13+6x4

16 = 14x - 13

16 + 13 = 14x

x = 29/14 or 2.07

88.

If 8, p, q and 26 is an A.P. Find the values of p and q

A.

p = 14 and q = 14

B.

p = 20 and q = 14

C.

p = 20 and q = 20

D.

p = 14 and q = 20

Correct answer is D

The common difference is 6. Just add 6 to get the next term 8, 14, 20 and 26

89.

If y varies inversely as x and x = 3 when y =4. Find the value of x when y = 12

A.

4

B.

1

C.

2

D.

3

Correct answer is B

y = 1/x; y = kx

k =xy → 3 * 4 = 12

x = ky 

x = 1212 = 1

90.

Let (*) be a binary operation on a natural number defined by a * b = a - b + (ab)2, then find 3 * 5

A.

223

B.

232

C.

32

D.

-232

Correct answer is A

3 * 5 = 3 - 5 + (3 x 5)2

-2 + (15)2

-2 + 225 

= 223