JEE PYQ: Functions Question 20
Question 20 - 2020 (07 Jan Shift 1)
If $g(x) = x^2 + x - 1$ and $(g \circ f)(x) = 4x^2 - 10x + 5$, then $f\left(\frac{5}{4}\right)$ is equal to:
(1) $\frac{3}{2}$
(2) $-\frac{1}{2}$
(3) $\frac{1}{2}$
(4) $-\frac{3}{2}$
Type: MCQ
Show Answer
Answer: (2) $-\frac{1}{2}$
Solution
$\left(f\left(\frac{5}{4}\right) + \frac{1}{2}\right)^2 = 0 \Rightarrow f\left(\frac{5}{4}\right) = -\frac{1}{2}$