WAEC Past Questions and Answers - Page 3924

19,616.

Simplify \(\frac{1}{x-3}-\frac{3(x-1)}{x^2 - 9}\)

A.

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

B.

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

C.

\(\frac{x-1}{x+3}\)

D.

\(\frac{4x}{x^2-9}\)

Correct answer is B

\(\frac{1}{x-3}-\frac{3(x-1)}{x^2 - 9}\\
\frac{1}{x-3}-\frac{3(x-1)}{(x-3)(x+3)}\\
\frac{x+3-3x+3}{(x-3)(x+3)};\frac{-2x+6}{(x-3)(x+3)}\\
\frac{-2(x-3)}{(x-3)(x+3)}=\frac{-2}{x+3}\)

19,617.

Given that (2x + 7) is a factor of \(2x^2 + 3x - 14\), find the other factor

A.

x + 2

B.

2 - x

C.

x - 2

D.

x + 1

Correct answer is C

\(2x^2 + 3x - 14\)

\(2x^2 + 7x - 4x - 14\)

\(x(2x + 7) - 2(2x + 7)\)

= \((x - 2)(2x + 7)\)

The other factor = (x - 2).

19,618.

If x varies inversely as y and \(x = \frac{2}{3}\) when y = 9, find the value of y when \(x=\frac{3}{4}\)

A.

\(\frac{1}{18}\)

B.

\(\frac{8}{81}\)

C.

\(\frac{9}{2}\)

D.

8

Correct answer is D

\(x \propto \frac{1}{y}\)

\(x = \frac{k}{y}\)

\(\frac{2}{3} = \frac{k}{9}\)

\(3k = 18 \implies k = 6\)

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

When y = \(\frac{3}{4}\),

x = \(\frac{6}{\frac{3}{4}}\)

= \(\frac{6 \times 4}{3}\)

= 8

19,619.

Given that \(27^{(1+x)}=9\) find x

A.

-3

B.

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

C.

\(\frac{5}{3}\)

D.

2

Correct answer is B

\(27^{(1+x)}=9\\
3^{3(1+x)}=3^2\\
3(1+x)=2\\
3+3x = 2\\
3x = -1
x = \frac{-1}{3}\)

19,620.

Given that \(x = -\frac{1}{2}and \hspace{1mm} y = 4 \hspace{1mm} evaluate \hspace{1mm} 3x^2y+xy^2\)

A.

-5

B.

-1

C.

4

D.

11

Correct answer is A

\(x = -\frac{1}{2}, y = 4\\
3x^2y + xy^2\\
3\left[-\frac{1}{2}\right]^2 \times 4 \times + \left(\frac{-1}{2}\right)(4)^2\\
3\times \frac{1}{4} \times 4 -\frac{1}{2} \times 16\\
3-8 = -5\)