JAMB Mathematics Past Questions & Answers - Page 249

1,241.

If f(x - 4) = x2 + 2x + 3, Find, f(2)

A.

6

B.

11

C.

27

D.

51

Correct answer is D

f(x - 4) = x2 + 2x + 3

To find f(2) = f(x - 4)

= f(2)

x - 4 = 2

x = 6

f(2) = 62 + 2(6) + 3

= 36 + 12 + 3

= 51

1,242.

If a = 2, b = -2 and c = -\(\frac{1}{2}\), evaluate (ab2 - bc2)(a2c - abc)

A.

2

B.

-28

C.

-30

D.

-34

Correct answer is D

(ab2 - bc2)(a2c - abc)

[2(2)2 - (- 2x\(\frac{1}{2}\))] [22(-\(\frac{1}{2}\)) - 2(-2)(-\(\frac{1}{2}\))]

[8 = \(\frac{1}{2}\)][-2 - 2] = \(\frac{17}{2}\) x 42

= -34

1,243.

Simplify (\(\frac{1}{x^{-1}} + \frac{1}{y^{-1}}\))-1

A.

\(\frac{x}{y}\)

B.

xy

C.

\(\frac{x}{y}\)

D.

(xy)-1

Correct answer is C

Simplify (\(\frac{1}{x^{-1}} + \frac{1}{y^{-1}}\))-1 = (\(\frac{1}{x^{-1}} + \frac{1}{y^{-1}}\))-1

= (x + y)-1 = \(\frac{(x)}{y}\)

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

1,244.

Simplify 3 log69 + log612 + log664 - log672

A.

5

B.

7776

C.

log631

D.

(7776)6

Correct answer is A

3 log69 + log612 + log664 - log672

= log693 + log612 + log664 - log672

log6729 + log612 + log664 - log672

log6(729 x 12 x 64) = log6776

= log665 = 5 log66 = 5

N.B: log66 = 1

1,245.

Simplify \(\sqrt{27}\) + \(\frac{3}{\sqrt{3}}\)

A.

4\(\sqrt{3}\)

B.

\(\frac{4}{\sqrt{3}}\)

C.

3\(\sqrt{3}\)

D.

\(\frac{\sqrt{3}}{4}\)

Correct answer is A

\(\sqrt{27}\) + \(\frac{3}{\sqrt{3}}\)

= \(\sqrt{9 \times 3}\) + \(\frac{3 \times {\sqrt{3}}}{{\sqrt{3}} \times {\sqrt{3}}}\)

= 3\(\sqrt{3}\) + \(\sqrt{3}\)

= 4\(\sqrt{3}\)