WAEC Further Mathematics Past Questions & Answers - Page 111

551.

If \((x + 2)\) and \((3x - 1)\) are factors of \(6x^{3} + x^{2} - 19x + 6\), find the third factor.

A.

\(2x - 3\)

B.

\(3x + 1\)

C.

\(x - 2\)

D.

\(3x + 2\)

Correct answer is A

To get the third factor, take the product of the other 2 factors and then divide the main equation by their product.

552.

Using the binomial expansion \((1+x)^{6} = 1 + 6x + 15x^{2} + 20x^{3} + 15x^{4} + 6x^{5} + x^{6}\), find, correct to 3 dp, the value of \((1.98)^{6}\)

A.

64.245

B.

61.255

C.

60.255

D.

60.245

Correct answer is C

\((1.98)^{6} = (1 + 0.98)^{6} = 1 + 6(0.98) + 15(0.98)^{2} + 20(0.98)^{3} + 15(0.98)^{4} + 6(0.98)^{5} + (0.98)^{6}\)

 \(\approxeq 1 + 5.88 + 14.406 + 18.823 + 13.836 + 5.424 + 0.886 \)

= \(60.255\)

553.

Simplify \(\frac{1 + \sqrt{8}}{3 - \sqrt{2}}\)

A.

\(7 + \sqrt{2}\)

B.

\(7 + 7\sqrt{2}\)

C.

\(1 - 7\sqrt{2}\)

D.

\(1 + \sqrt{2}\)

Correct answer is D

\(\frac{1 + \sqrt{8}}{3 - \sqrt{2}}\)

Rationalizing by multiplying through with \(3 + \sqrt{2}\),

\((\frac{1 + \sqrt{8}}{3 - \sqrt{2}})(\frac{3 + \sqrt{2}}{3 + \sqrt{2}}) = \frac{3 + \sqrt{2} + 3\sqrt{8} + 4}{9 - 2}\)

= \(\frac{3 + \sqrt{2} + 3\sqrt{4 \times 2} + 4}{7} \)

= \(\frac{7 + 7\sqrt{2}}{7} = 1 + \sqrt{2}\)

554.

If \(8^{x} ÷ (\frac{1}{4})^{y} = 1\) and \(\log_{2}(x - 2y) = 1\), find the value of (x - y)

A.

\(\frac{5}{4}\)

B.

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

C.

\(1\)

D.

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

Correct answer is A

\(8^{x} ÷ (\frac{1}{4})^{y} = 1\)

\((2^{3})^{x} ÷ (2^{-2})^{y} = 2^{0}\)

\(2^{3x - (-2y)} = 2^{0}\)

\(\implies 3x + 2y = 0 .... (1)\)

\(\log_{2}(x - 2y) = 1\)

\( x - 2y = 2^{1} = 2 ..... (2)\)

Solving equations 1 and 2,

\(x = \frac{1}{2}, y = \frac{-3}{4}\)

\((x - y) = \frac{1}{2} - \frac{-3}{4} = \frac{5}{4}\)

555.

If \(f(x) = 3x^{3} + 8x^{2} + 6x + k\) and \(f(2) = 1\), find the value of k.

A.

-67

B.

-61

C.

61

D.

67

Correct answer is A

\(f(x) = 3x^{3} + 8x^{2} + 6x + k\)

\(f(2) = 3(2^{3}) + 8(2^{2}) + 6(2) + k = 1\)

\(\implies 24 + 32 + 12 + k = 1\)

\(68 + k = 1  \therefore k = 1 - 68 = -67\)