If `f(x)=ax+bandg(x)=cx+d` such that `f[g(x)]=g[f(x)]` then which one of the following is correct?

If f(x)=ax+b and g(x)=cx+d are such that (fog)(x)=(gof)(x) , then which one of the following is correct ?

If g(x)=(1)/(f(x))andf(x)=x,xne0 , then which one of the following is correct

If f(x)=x^2 and g(x)=x^2+1 then: (f@g)(x)=(g@f)(x)=

if f(x) =ax +b and g(x) = cx +d , then f[g(x) ] - g[f(x) ] is equivalent to

If f(x) = ax + b and g(x) = cx + d, then f(g(x))=g(f(x)) implies

If f(x)=ax+b and g(x)=cx+d, then f(g(x))=g(f(x)) is equivalent to

If f(x)=ax+b and g(x)=cx+d, then f(g(x))=g(f(x)) is equivalent to

If f(x)=ax+b and g(x)=cx+d, then f(g(x))=g(f(x)) is equivalent to

If f(x)=7x+12 and f(g(x))=21x^(2)+40 , then which of the following is g(x) ?