WAEC Mathematics Past Questions & Answers - Page 140

696.

Factorize x2 - 2x - 3xy completely

A.

(x - 2)(3x - y)

B.

(x - 3y)(x - 2)

C.

(x - 3y)(x - 3y)

D.

(3x + y)(x - 2)

Correct answer is B

x2 - 2x - 3xy + 6y = x(x - 2) -3y(x - 2)

= (x - 3y)(x - 2)

697.

If (2x + 3)3 = 125, find the value of x

A.

1

B.

2

C.

3

D.

4

Correct answer is A

(2x + 3 )2 = 125

2n + 3 = 3\(\sqrt{125}\)

2x + 3 = 5

2x = 5 - 3

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

= 1

698.

If \(\frac{3}{2x} - \frac{2}{3x} = 4\), solve for x

A.

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

B.

\(\frac{4}{13}\)

C.

\(\frac{5}{24}\)

D.

\(\frac{13}{24}\)

Correct answer is C

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

\(\frac{9 - 4}{6x}\); \(\frac{5}{6x}\) = 4

5 = 24x ; x = \(\frac{5}{24}\)

699.

Two sets are disjoint if

A.

they are both empty

B.

their union is an empty set

C.

their intersection is an empty set

D.

one of them is a subset of the other

Correct answer is C

No explanation has been provided for this answer.

700.

Express the square root of 0.000144 in the standard form

A.

1.2 x 10-4

B.

1.2 x 10-3

C.

1.2 x 10-2

D.

1.2 x 10-1

Correct answer is C

\(\sqrt{0.000144}\) = 0.012

= 1.2 x 10-2