Mock Test 420 If fx 2x2 and 2f3a 144 then what could be th

Mock Test 4/20 If f(x) = 2x2, and 2f(3a) = 144, then what could be the value of a? 2

Solution

Given that

f(x) = 2x²

To find the value of f(3a), substitute x = 3a in 3x²

Hence,

f(3a) = 2(3a)²

= 2.9a²

f(3a) = 18a²

Then,

2f(3a)= 2.18a² =  36a²

Given that 2f(3a) = 144

36a² = 144

a² = 144/36

a² = 4

a = 4

a = ± 2

a = +2 or -2

Since -2 is not listed as an answer,

2 is the correct answer.

Hence,

(D) is the answer.