WAEC Further Mathematics Past Questions & Answers - Page 79

391.

If \(\sin x = -\sin 70°, 0° < x < 360°\), determine the two possible values of x.

A.

110°, 250°

B.

110°, 290°

C.

200°, 250°

D.

250°, 290°

Correct answer is D

The value of the sine of an angle is negative in the third and fourth quadrant. Hence options A and B are not the options.

\(\sin 250 = -\sin (250 - 180) = - \sin 70\)

\(\sin 290 = - \sin (360 - 290) = - \sin 70\)

392.

If (x - 3) is a factor of \(2x^{2} - 2x + p\), find the value of constant p.

A.

-12

B.

-6

C.

3

D.

6

Correct answer is A

Using remainder theorem, since x - 3 is a factor, then 

given \(2x^{2} - 2x + p\), f(3) = 0

\(2(3^{2}) - 2(3) + p = 0 \implies 18 - 6 = -p\)

\(p = -12\)

393.

The roots of a quadratic equation are \((3 - \sqrt{3})\) and \((3 + \sqrt{3})\). Find its equation.

A.

\(x^{2} - 6x - 9 = 0\)

B.

\(x^{2} - 6x + 6 = 0\)

C.

\(x^{2} + 6x - 9 = 0\)

D.

\(x^{2} + 6x + 6 = 0\)

Correct answer is B

\((x - \alpha)(x - \beta) = 0\)

\((x - (3 - \sqrt{3}))(x - (3 + \sqrt{3})) = 0\)

\((x^{2} - (3 - \sqrt{3})x - (3 + \sqrt{3})x + (9 + 3\sqrt{3} - 3\sqrt{3} - 3) = 0\)

\(x^{2} - 3x - x\sqrt{3} - 3x + x\sqrt{3} + 6 = 0\)

\(x^{2} - 6x + 6 = 0\)

394.

The coefficient of the 7th term in the binomial expansion of \((2 - \frac{x}{3})^{10}\) in ascending powers of x is

A.

\(\frac{560}{243}\)

B.

\(\frac{841}{243}\)

C.

\(\frac{1120}{243}\)

D.

\(\frac{4481}{243}\)

Correct answer is C

\(^{10}C_{7 - 1} (2^{10 - 6}) (\frac{-1}{3})^{6}\)

\(\frac{10!}{(10 - 6)! 6!} \times 16 \times \frac{1}{243} \)

= \(210 \times 16 \times \frac{1}{729} \)

= \(\frac{1120}{243}\)

395.

Simplify \(\frac{\log_{5} 8}{\log_{5} \sqrt{8}}\).

A.

-2

B.

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

C.

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

D.

2

Correct answer is D

\(\frac{\log_{5} 8}{\log_{5} \sqrt{8}} = \frac{\log_{5} 8}{\log_{5} 8^{\frac{1}{2}}}\)

= \(\frac{\log_{5} 8}{\frac{1}{2}\log_{5} 8}\)

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

= 2