C3 HW help

Im stuck on this question:

Show that the composite function gf is (8x^3 - 1) / (1 - 2x^3)

f(x)= 1 - 2x^3
g(x)=(3/x) - 4

I subbed f into g but didnt get it
any help appreciated


also, solve gf(x)=0, if i set it = 0 then i cant bring anything across, do i have to factorise and cancel down the bottom maybe?

Im stuck on this question:

Show that the composite function gf is (8x^3 - 1) / (1 - 2x^3)

also, solve gf(x)=0, if i set it = 0 then i cant bring anything across, do i have to factorise and cancel down the bottom maybe?

You need to put 1-2x^3 where the x is in g(x) and then put it all over the same denominator

i did and i didnt get the same answer

Did you get this? You'd only have to distribute and simplify.

$g\circ f(x)=g(f(x))=g(1-2x^{ 3 })=\frac { 3 }{ 1-2x^{ 3 } } -4=\frac { 3-4(1-2x^{ 3 }) }{ 1-2x^{ 3 } }$