WAEC Further Mathematics Past Questions & Answers - Page 57

281.

Given that the straight lines \(kx - 5y + 6 = 0\) and \(mx + ny - 1 = 0\) are parallel, find a relationship connecting the constants m, n and k.

A.

5n - km = 0

B.

kn + 5m = 0

C.

5n + km = 0

D.

kn - 5m = 0

Correct answer is B

Two lines are parallel if and only if their slopes are equal.

\(kx - 5y + 6 = 0 \implies 5y = kx + 6\)

\(y = \frac{k}{5}x + \frac{6}{5}\)

\(Slope = \frac{k}{5}\)

\(mx + ny - 1 = 0 \implies ny = 1 - mx\)

\(y = \frac{1}{n} - \frac{m}{n}x\)

\(Slope = -\frac{m}{n}\)

\(Parallel \implies \frac{k}{5} = -\frac{m}{n}\)

\(-5m = kn \implies 5m + kn = 0\)

282.

In the diagram above, forces P, Q and 50N are acting on a body at M. If the system is in equilibrium, calculate, in terms of \(\theta\), the magnitude of P.

A.

\(\frac{50 \cos \theta}{\sin (\theta + 45)°}\)

B.

\(\frac{50 \cos \theta}{\cos (\theta + 45)°}\)

C.

\(\frac{50 \sin \theta}{\cos (\theta + 45)°}\)

D.

\(\frac{50 \sin \theta}{\sin (\theta + 45)°}\)

Correct answer is D

No explanation has been provided for this answer.

283.

The distance between P(x, 7) and Q(6, 19) is 13 units. Find the values of x.

A.

1 or -7

B.

1 or 7

C.

1 or 11

D.

5 or -5

Correct answer is C

\(d = \sqrt{(x_{1} - x_{2})^{2} + (y_{1} - y_{2})^{2}}\)

\(13 = \sqrt{(x - 6)^{2} + (7 - 19)^{2}}\)

\(13^{2} = x^{2} - 12x + 36 + 144\)

\(169 = x^{2} - 12x + 180\)

\(x^{2} - 12x + 180 - 169 = 0 \implies x^{2} - 12x + 11 = 0\)

\((x - 1)(x - 11) = 0 \implies x = \text{1 or 11}\)

284.

If \(y = x^{2} - 6x + 11\) is written in the form \(y = a(x - h)^{2} + k\), find the value of \((a + h + k)\).

A.

-4

B.

-3

C.

0

D.

6

Correct answer is D

\(y = x^{2} - 6x + 11\)

\( y = a(x - h)^{2} + k\)

\(a(x - h)^{2} + k = a(x^{2} - 2hx + h^{2}) + k\)

\(ax^{2} - 2ahx + ah^{2} + k = x^{2} - 6x + 11\)

Comparing, we have

\(a = 1\)

\(2ah = 6 \implies 2h = 6; h = 3\)

\(ah^{2} + k = 11 \implies (1 \times 3^{2}) + k = 11\)

\(9 + k = 11 \implies k = 2\)

\(\therefore a + h + k = 1 + 3 + 2 = 6\)

285.

The initial and final velocities of an object of mass 5 kg are \(u = \begin{pmatrix} 1 \\ 3 \end{pmatrix}\) and \(v = \begin{pmatrix} 4 \\ 7 \end{pmatrix}\) respectively. Find the magnitude of its change in momentum.

A.

25

B.

15

C.

\(3\sqrt{7}\)

D.

\(\sqrt{10}\)

Correct answer is A

Change in momentum = m (v - u)

= \(5 \times (\begin{pmatrix} 4 \\ 7 \end{pmatrix} - \begin{pmatrix} 1 \\ 3 \end{pmatrix})\)

= \(5 \times \begin{pmatrix} 3 \\ 4 \end{pmatrix}\)

= \(\begin{pmatrix} 15 \\ 20 \end{pmatrix}\)

\(|m(v - u)| = \sqrt{15^{2} + 20^{2}} = \sqrt{625} = 25\)