WAEC Mathematics Past Questions & Answers - Page 311

1,551.

Solve: 6(x - 4) + 3(x + 7) = 3

A.

3/2

B.

2/3

C.

1/2

D.

1/3

Correct answer is B

6(x - 4) + 3(x + 7) = 3

6x - 24 + 3x + 21 = 3

9x - 3 = 3

9x = 6

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

1,552.

Find the equation whose roots are -2/3 and -1/4

A.

12x2 + 11x + 2 = 0

B.

12x2 - 11x + 2 = 0

C.

x2 - 11/12x + 2 = 0

D.

12x2 - 11x - 2 = 0

E.

x2 - 11/12x - 2 = 0

Correct answer is A

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

\(\implies (x + \frac{2}{3}) = 0; (x + \frac{1}{4}) = 0\)

\((x + \frac{2}{3})(x + \frac{1}{4}) = 0\)

\(x^{2} + \frac{1}{4}x + \frac{2}{3}x + \frac{1}{6} = 0\)

\(x^2 + \frac{11}{12}x + \frac{1}{6} = 0\)

\(12x^2 + 11x + 2 = 0\)

1,553.

Simplify: 1/4(2n - 2n+2)

A.

2n2 - 2n

B.

2n-2(1-2n)

C.

2n + 22n + 2

D.

22n

Correct answer is A

1/4(2n - 2n+2) = 2-2(2n - 2n x 22) = 2n x -2(1 - 22)= 22n-2
(20 - 22) = 22n-2 - 2n

1,554.

Simplify \((\frac{3}{x} + \frac{15}{2y}) \div \frac{6}{xy}\)

A.

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

B.

\(\frac{9(2x - 5x)}{x^2y^2}\)

C.

\(\frac{5x - 2y}{2}\)

D.

\(\frac{c^2y^2}{18y - 45x}\)

E.

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

Correct answer is A

\((\frac{3}{x} - \frac{15}{2y}) \div \frac{6}{xy}\)

= \((\frac{6y - 15x}{2xy}) \div \frac{6}{xy}\)

= \(\frac{6y - 15x}{2xy} \times \frac{xy}{6}\)

= \(\frac{3(2y - 5x)}{2xy} \times \frac{xy}{6}\)

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

1,555.

Solve the equation: 3a + 10 = a\(^2\)

A.

a = 5 or a = 2

B.

a = -5 or a = 2

C.

a = 10 or a = 0

D.

a = 5 or a = 0

E.

a = 5 or a = -2

Correct answer is E

3a + 10 = a\(^2\)

a\(^2\) - 3a - 10 = 0

a\(^2\) - 5a + 2a - 10 = 0

a(a - 5) + 2(a - 5) = 0

(a - 5)(a + 2) = 0

a = 5 or a = -2.