JEE Main 2017 — Functions Question with Solution
From: JEE Main 2017 (Online) 8th April Morning Slot
Question
Let f(x) = 210.x + 1 and g(x)=310.x 1. If (fog) (x) = x, then x is equal to :
Choose an option
Show full solutionCorrect option: D
Correct answer
D
Step-by-step explanation
(fog) (x) = x
f (g(x)) = x
f (310. x 1) = x [ as g(x) = 310. x 1]
210 . (310 . x 1) + 1 = x
310 . x 1 + 210 = x . 210 [dividing by 210]
310 . x 210 . x = 1 210
x (310 2 10) = 1 210
x =
f (g(x)) = x
f (310. x 1) = x [ as g(x) = 310. x 1]
210 . (310 . x 1) + 1 = x
310 . x 1 + 210 = x . 210 [dividing by 210]
310 . x 210 . x = 1 210
x (310 2 10) = 1 210
x =
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This is a previous-year question from JEE Main 2017, covering the Functions chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.