Let f(x) and g(x) be two bijective functions, where f(x)=3x+5 and g(x)=ex3−2 , then (fog(x))−1 is equal to
A
lnx
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B
ln(1−x)
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C
ln(1+x)
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D
ex+1
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Solution
The correct option is Cln(1+x) Given: f(x)=3x+5 and g(x)=ex3−2 ⇒fog(x)=ex−6+5⇒fog(x)=ex−1
Let y=(fog(x))=ex−1 ⇒1+y=ex⇒x=ln(1+y)
Replace x with y, we get (fog(x))−1=ln(1+x)