WAEC Mathematics Past Questions & Answers - Page 148

736.

Simplify: \(\frac{2x^2 - 5x - 12}{4x^2 - 9}\)

A.

\(\frac{x + 4}{2x + 3}\)

B.

\(\frac{x + 4}{2x - 3}\)

C.

\(\frac{x - 4}{2x + 3}\)

D.

\(\frac{x - 4}{2x - 3}\)

Correct answer is D

\(\frac{2x^2 - 5x - 12}{4x^2 - 9}\) = \(\frac{3x^2 - 8x + 3x - 12}{(2x)^2 - 3^2}\)

= \(\frac{32(x - 4) + 3(x - 4)}{(2x - 3)(2x + 3)} - \frac{(x - 4) + (2x + 3)}{(2x - 3) (2x + 3)}\)

= \(\frac{x - 4}{2x - 3}\)

737.

If p = \(\frac{3}{5} \sqrt{\frac{q}{r}}\), express q in terms of p and r

A.

\(\frac{9}{25} pr^2\)

B.

\(\frac{9}{25} p^2r\)

C.

\(\frac{25}{9} p^2r\)

D.

\(\frac{25}{9} pr^2\)

Correct answer is C

p = \(\frac{3}{5} \sqrt{\frac{q}{r}}; \frac{5p}{3} = \sqrt{\frac{q}{r}}\)

= (\(\frac{5}{3}p\))2

= \(\frac{q}{r}\)

= \(\frac{25p^2}{9} = \frac{q}{r}\)

q = \(\frac{25}{9} p^2 r\)

738.

If 4y is 9 greater than the sum of y and 3x, by how much is y greater than x?

A.

3

B.

6

C.

9

D.

12

Correct answer is A

4y - 9 > y + 3x; 4y - y > 3x + 9

3y > 3(x + 3); y = > \(\frac{3(x + 3)}{3}\)

y > x + 3; y - 3 > x

y is greater than x by 3

739.

Factorize 5y2 + 2ay - 3a2

A.

(a - y)(5y - 3a)

B.

(y - a)(5y - 3a)

C.

(y - a)(5y + 3a)

D.

(y + a)(5y - 3a)

Correct answer is D

5y2 + 2ay - 3a2 = 5y2 + 5ay - 3a2

= 5y(y + a) - 3a(y + a)

= (y + a)(5y - 3a)

740.

Given that x = 2 and y = -\(\frac{1}{4}\), evaluate \(\frac{x^2y - 2xy}{5}\)

A.

zero

B.

\(\frac{1}{5}\)

C.

1

D.

2

Correct answer is A

Given; x = 2; y = \(\frac{-1}{4}\)

= \(\frac{x^2y - 2xy}{5}\)

= \(\frac{2^2(\frac{-1}{4}) - 2(2)(\frac{-1}{4})}{5}\)

= \(\frac{4(\frac{-1}{4}) + 4(\frac{-1}{4})}{5}\)

= \(\frac{1 + 1}{5}\)

= \(\frac{0}{5}\)

= 0