Class 12 Relations And Functions · Mcq Single Correct1 Markstypes_of_functions
Class 12 Maths · Relations And Functions · Mcq Single Correct #72
The function \(f:\mathbb R\to\mathbb R\) defined by \(f(x)=2^x+2^{|x|}\) is
(A) One-one and onto
(B) Many-one and onto
(C) One-one and into
(D) Many-one and into
✅ Step-by-Step Solution
Final Answer: Option (D): Many-one and into
For \(x<0\), write \(t=2^x\in(0,1)\). Then \(f(x)=t+t^{-1}\) decreases towards 2 as \(x\to0^-\). For \(x\ge0\), \(f(x)=2^{x+1}\) increases from 2. Its range is \([2,\infty)\), and \(f(-1)=5/2=f(\log_2(5/4))\), so it is many-one and into.
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