We have, f(x+2x−4)=2x+1
Let x+2x−4=X⇒xX+2X=x−4⇒x(X−1)=−4−2X⇒x=(1−X)2(2+X)
Putting x=(1−X)2(2+X) in the given functional equation, we get
⇒f(X)=2×21−X2+X+1=1−X8+4X+1−X=1−X3X+9=(1−X)3(X+3)
Replacing X→x, we get
f(x)=(1−x)3(x+3)
⇒∫f(x)dx=3∫(1−xx+3)dx=3∫1−x4−(1−x)dx=3∫1−x4dx−∫dx
=−12ln∣1−x∣−3x+C, where C is the constant of integration.