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WAEC Further Mathematics Past Questions & Answers - Page 80

396.

If 163x=14(32x1), find the value of x.

A.

1

B.

13

C.

37

D.

519

Correct answer is A

163x=14(32x1)

(24)3x=(22)((25)x1)

212x=22+5x5

12x=7+5x

7x=7x=1

397.

If 5288=m2, where m is a constant. Find m.

A.

112

B.

114

C.

214

D.

212

Correct answer is C

52=5×22×2=522

88=228=24

5288=(5214)2

= 942

= 2142

398.

Find the value of \cos(60° + 45°) leaving your answer in surd form

A.

\frac{6 + \sqrt{2}}{4}

B.

\frac{3 + \sqrt{6}}{4}

C.

\frac{\sqrt{2} - \sqrt{6}}{4}

D.

\frac{3 - \sqrt{6}}{4}

Correct answer is C

\cos (x + y) = \cos x \cos y - \sin x \sin y

\cos (60 + 45) = \cos 60 \cos 45 - \sin 60 \sin 45

= \frac{1}{2} \times \frac{\sqrt{2}}{2} - \frac{\sqrt{3}}{2} \times \frac{\sqrt{2}}{2}

= \frac{\sqrt{2} - \sqrt{6}}{4}

399.

Find the domain of f(x) = \frac{x}{3 - x}, x \in R, the set of real numbers.

A.

{x : x \in R, x \neq 3}

B.

{x : x \in R, x \neq 1}

C.

{x : x \in R, x \neq 0}

D.

{x : x \in R, x\neq -3}

Correct answer is A

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

f(x) has a defined value except at x = 3 where the function is undefined.

400.

Find, correct to two decimal places, the acute angle between p = \begin{pmatrix} 13 \\ 14 \end{pmatrix} and q = \begin{pmatrix} 12 \\ 5 \end{pmatrix}.

A.

23.52°

B.

24.50°

C.

29.52°

D.

29.82°

Correct answer is B

p . q = |p||q|\cos \theta

156 + 70 = (\sqrt{13^{2} + 14^{2}})(\sqrt{12^{2} + 5^{2}}) \cos \theta

226 = (\sqrt{365})(13) \cos \theta

\frac{226}{13\sqrt{365}} = \cos \theta

\cos \theta = 0.9099

\theta = 24.50°