WAEC Further Mathematics Past Questions & Answers - Page 46

226.

Evaluate \(\lim \limits_{x \to 1} \frac{1 - x}{x^{2} - 3x + 2}\)

A.

1

B.

\(\frac{1}{2}\)

C.

0

D.

-1

Correct answer is A

\(\lim \limits_{x \to 1} \frac{1 - x}{x^{2} - 3x + 2}\)

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

= \(\frac{-1}{x - 2}\)

\(\lim \limits_{x \to 1} \frac{1 - x}{x^{2} - 3x + 2} = \lim \limits_{x \to 1} \frac{-1}{x - 2}\)

= \(\frac{-1}{1 - 2} = \frac{-1}{-1} = 1\)

227.

Evaluate \(\log_{0.25} 8\)

A.

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

B.

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

C.

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

D.

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

Correct answer is D

\(\log_{0.25} 8 = x\)

\(8 = 0.25^{x}\)

\(2^{3} = (2^{-2})^{x} \implies 3 = -2x\)

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

228.

Find the sum of the exponential series \(96 + 24 + 6 +...\)

A.

144

B.

128

C.

72

D.

64

Correct answer is B

\(S_{\infty} = \frac{a}{1 - r}\) (for an exponential series)

\(r = \frac{24}{96} = \frac{6}{24} = \frac{1}{4}\)

\(S_{\infty} = \frac{96}{1 - \frac{1}{4}} = \frac{96}{\frac{3}{4}}\)

= \(\frac{96 \times 4}{3} = 128\)

229.

The roots of the equation \(2x^{2} + kx + 5 = 0\) are \(\alpha\) and \(\beta\), where k is a constant. If \(\alpha^{2} + \beta^{2} = -1\), find the values of k.

A.

\(\pm 16\)

B.

\(\pm 8\)

C.

\(\pm 4\)

D.

\(\pm 2\)

Correct answer is C

\(2x^{2} + kx + 5 = 0\)

\(\alpha + \beta = \frac{-b}{a} = \frac{-k}{2}\)

\(\alpha \beta = \frac{c}{a} = \frac{5}{2}\)

\(\alpha^{2} + \beta^{2} = (\alpha + \beta)^{2} - 2\alpha \beta\)

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

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

\(k^{2} = 16 \therefore k = \pm 4\)

230.

Find the equation of the line passing through (0, -1) and parallel to the y- axis.

A.

y = -1

B.

y = 0

C.

x = 0

D.

x = -1

Correct answer is C

No explanation has been provided for this answer.