WAEC Mathematics Past Questions & Answers - Page 276

1,376.

Find the value(s) of x for which the expression is undefined: \(\frac{6x - 1}{x^2 + 4x - 5}\)

A.

+4 or+1

B.

-5 or +1

C.

-5 or -1

D.

+5 or -1

E.

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

Correct answer is B

\(\frac{6x - 1}{x^2 + 4x - 5}\)

The expression is undefined when \(x^2 + 4x - 5 = 0\)

\(x^2 + 5x - x - 5 = 0\)

\(x(x + 5) - 1(x + 5) = 0\)

\((x - 1)(x + 5) = 0\)

The expression is undefined when x = 1 or -5.

1,377.

If R = [2, 4, 6, 7] and S = [1, 2, 4, 8], then R∪S equal

A.

[1,2,4,6,7,8]

B.

[1,2,4,7,8]

C.

[1,4.7,8]

D.

[2.6.7]

E.

[2.4]

Correct answer is A

R = {2, 4, 6, 7}; S = {1, 2, 4, 8}

R \(\cup\) S = {1, 2, 4, 6, 7, 8}

1,378.

lf 16/9 , x, 1, y are in Geometric Progression (GP), find the product of x and y.

A.

9/16

B.

3/4

C.

1

D.

4/3

E.

16/6

Correct answer is C

16/9, x, 1, y => a, ar, ar2, ar3
ar2 = 1 => 16r2/9 = 1 => 16r2
9 => r2 = 9/16 => r = 3/4
ar2 = y = ar2 x r = 1 x 3/4 = 3/4
x xy = 4/3 x 3/4 = 1

1,379.

Find the nth term Un of the A.P., 11, 4, -3,....... .

A.

Un=19+7n

B.

Un=19-7n

C.

Un=18+7n

D.

Un= 18-7n

E.

Un= 17-7n

Correct answer is D

A.P 11, 4, -3
1st term = 11
A.P = a, a + d, a + 2d ...... a + (n - 1)d
If a = 11
a + d = 4
d = 4 - 11 = -7
nth term = a + (n-1)d
         = 11 + (n-1)(-7)
         = 11 - 7n + 7
         = 18 - 7n

1,380.

By selling some crates of soft drinks for N600.00, a dealer makes a profit of 50%. How much did the dealer pay for the drinks?

A.

N1,200.00

B.

N900.00

C.

N450.00

D.

N400.00

E.

N200.00

Correct answer is D

S.P = N600.00

(100 + 50)% = N600

150% = N600

1% = \(\frac{600}{150}\)

100% = \(\frac{600}{150} \times 100%\)

= N400