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Question: Answered & Verified by Expert
Let fx=210x+1 and gx=310x-1. If fogx=x, then x is equal to:
MathematicsFunctionsJEE MainJEE Main 2017 (08 Apr Online)
Options:
  • A 210-1210-3-10
  • B 1-2-10310-2-10
  • C 310-1310-2-10
  • D 1-3-10210-3-10
Solution:
1295 Upvotes Verified Answer
The correct answer is: 1-2-10310-2-10

Given fgx=x

Where,fx=210x+1 ,gx=310x-1.

f310x-1=210310x-1+1

210310x-1+1=x

x610-1=210-1

x=210-1610-1=210-1210(2×3)10-1210

=1-2-10310-2-10

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