f(x) = 9x^3+2x^2-5x+4 and g(x) = 5x^3 -7x+4

What is f(x) - g(x)? Write the final answer in factored form.

2 answers

I am really having trouble with this one. Please help.
f(x) - g(x ) =

9 x^3 + 2 x^2 - 5 x + 4 - ( 5 x^3 - 7 x + 4 ) =

9 x^3 + 2 x^2 - 5 x + 4 - 5 x^3 - ( - 7 x ) - 4 =

9 x^3 + 2 x^2 - 5 x + 4 - 5 x^3 + 7 x - 4 =

9 x^3 - 5 x^3 + 2 x^2 - 5 x + 7 x + 4 - 4 =

4 x^3 + 2 x^2 + 2 x =

2 x * 2 x^2 + 2 x * x + 2 x * 1 =

2 x * ( 2 x^2 + x + 1 )