Question

13(a). Two functions, f and g, are defined by f:x→2x²−1 and g:x→3x+2, where x is a real number. (i) If f(x−1)−7=0, find the values of x; (ii) Evaluate f(−½)·g(3) / (f(4)−g(5)).

Accepted Answer

(i) f(x−1) = 2(x−1)²−1 = 7 ⟹ (x−1)²=4 ⟹ x−1=±2 ⟹ x=3 or x=−1
(ii) f(−½)=2(¼)−1=−0.5; g(3)=3(3)+2=11; f(4)=2(16)−1=31; g(5)=3(5)+2=17
f(4)−g(5)=31−17=14
Result = (−0.5×11)/14 = −5.5/14 ≈ −0.39 (= −11/28)

WAEC Mathematics 2014 Theory — Question 22

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