WAEC Further Mathematics Past Questions & Answers - Page 43

211.

A and B are two independent events such that \(P(A) = \frac{2}{5}\) and \(P(A \cap B) = \frac{1}{15}\). Find \(P(B)\)

A.

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

B.

\(\frac{1}{3}\)

C.

\(\frac{1}{6}\)

D.

\(\frac{2}{15}\)

Correct answer is C

For independent events A and B, \(P(A \cap B) = P(A) \times P(B)\)

\(\frac{1}{15} = \frac{2}{5} \times P(B)\)

\(P(B) = \frac{1}{15} \div \frac{2}{5}\)

\(P(B) = \frac{1}{6}\)

212.

Find the coordinates of the centre of the circle \(4x^{2} + 4y^{2} - 5x + 3y - 2 = 0\).

A.

\((\frac{-5}{4}, \frac{3}{4})\)

B.

\((\frac{3}{8}, -\frac{5}{8})\)

C.

\((\frac{5}{8}, -\frac{3}{8})\)

D.

\((\frac{5}{4}, -\frac{3}{4})\)

Correct answer is C

Equation : \((x - a)^{2} + (y - b)^{2} = r^{2}\)

Expanding : \(x^{2} + y^{2} - 2ax - 2by + a^{2} + b^{2} = r^{2}\)

Given, \(4x^{2} + 4y^{2} - 5x + 3y - 2 = 0\)

Divide through by 4 to make the coefficient of \(x^{2}\) and \(y^{2}\) to be 1.

\(x^{2} + y^{2} - \frac{5}{4}x + \frac{3}{4}y - \frac{1}{2} = 0\)

Comparing, \(2a = \frac{5}{4} \implies a = \frac{5}{8}\)

\(2b = -\frac{3}{4} \implies b = -\frac{3}{8}\)

\((a, b) = (\frac{5}{8}, -\frac{5}{8})\)

213.

Given that \(\begin{pmatrix} 1 & -3 \\ 1 & 4 \end{pmatrix} \begin{pmatrix} -6 \\ P \end{pmatrix} = \begin{pmatrix} 3 \\ -26 \end{pmatrix}\), find the value of P.

A.

-8

B.

-5

C.

4

D.

-3

Correct answer is D

\(\begin{pmatrix} 1 & -3 \\ 1 & 4 \end{pmatrix} \begin{pmatrix} -6 \\ P \end{pmatrix} = \begin{pmatrix} 3 \\ -26 \end{pmatrix}\)

\(\implies (1 \times -6) + (-3 \times P) = 3\)

\(-6 - 3P = 3 \implies -3P = 9\)

\(P = -3\)

215.

Find the least value of the function \(f(x) = 3x^{2} + 18x + 32\)

A.

5

B.

4

C.

-3

D.

-2

Correct answer is A

\(f(x) = 3x^{2} + 18x + 32\)

\(\frac{\mathrm d y}{\mathrm d x} = 6x + 18 = 0\)

\(6x = -18 \implies x = -3\)

\(f(-3) = 3(-3^{2}) + 18(-3) + 32 = 27 - 54 + 32 = 5\)