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WAEC Further Mathematics Past Questions & Answers - Page 128

636.

Consider the statements:

p : Musa is short

q : Musa is brilliant

Which of the following represents the statement "Musa is short but not brilliant"?

A.

pq

B.

pq

C.

pq

D.

pq

Correct answer is C

No explanation has been provided for this answer.

637.

An operation * is defined on the set, R, of real numbers by pq=p+q+2pq. If the identity element is 0, find the value of p for which the operation has no inverse.

A.

12

B.

0

C.

23

D.

2

Correct answer is A

Given the formula for p * q as: p+q+2pq and its identity element is 0, such that if, say, t is the inverse of p, then

pt=0, then p+t+2pt=0

t = \frac{-1}{1 + 2p} is the formula for the inverse of p and is undefined on R when

1 + 2p) = 0 i.e when 2p = -1; p = \frac{-1}{2}.

638.

Express \frac{8 - 3\sqrt{6}}{2\sqrt{3} + 3\sqrt{2}} in the form p\sqrt{3} + q\sqrt{2}

A.

7\sqrt{3} - \frac{17\sqrt{2}}{3}

B.

7\sqrt{2} - \frac{17\sqrt{3}}{3}

C.

-7\sqrt{2} + \frac{17\sqrt{3}}{3}

D.

-7\sqrt{3} - \frac{17\sqrt{2}}{3}

Correct answer is B

Given \frac{8 - 3\sqrt{6}}{2\sqrt{3} + 3\sqrt{2}},

first, we rationalise  by multiplying through with 2\sqrt{3} - 3\sqrt{2} (the inverse of the denominator).

(\frac{8 - 3\sqrt{6}}{2\sqrt{3} + 3\sqrt{2}})(\frac{2\sqrt{3} - 3\sqrt{2}}{2\sqrt{3} - 3\sqrt{2}})

= \frac{16\sqrt{3} - 24\sqrt{2} - 18\sqrt{2} + 18\sqrt{3}}{4(3) - 6\sqrt{6} + 6\sqrt{6} - 9(2)}

= \frac{34\sqrt{3} - 42\sqrt{2}}{-6} = 7\sqrt{2} - \frac{17\sqrt{3}}{3}

639.

If P = {x : -2 < x < 5} and Q = {x : -5 < x < 2} are subsets of \mu = {x : -5 \leq x \leq 5}, where x is a real number, find (P \cup Q).

A.

{x : -5 < x < 5}

B.

{x : -5 \leq x \leq 5}

C.

{x : -5 \leq x < 5}

D.

{x : -5 < x \leq 5}

Correct answer is A

P = {x : -2 < x < 5} and Q = {x:  -5 < x < 2}

(P \cup Q) = {x : -5 < x < 5}

640.

Two functions f and g are defined on the set of real numbers by f : x \to x^{2} + 1 and g : x \to x - 2. Find f o g

A.

x^{2} + 4x - 5

B.

x^{2} - 4x + 5

C.

x^{2} - 1

D.

x - 1

Correct answer is B

f(x) = x^{2} + 1  and  g(x) = x - 2

f o g = f(g(x)) = f(x - 2) = (x - 2)^{2} + 1

= x^{2} - 4x + 4 + 1 = x^{2} - 4x + 5