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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