Answer: See below
Step-by-step explanation:
[tex]h\:\circ \:g=h\left(g\left(x\right)\right)[/tex]
[tex]=5\left(7x^2-4x-3\right)^2-12\left(7x^2-4x-3\right)[/tex]
[tex]=5\left(7x^2-4x-3\right)\left(7x^2-4x-3\right)-12\left(7x^2-4x-3\right)[/tex]
[tex]=245x^4-280x^3-130x^2+120x+45-84x^2+48x+36[/tex]
Simplify:
[tex]=245x^4-280x^3-214x^2+168x+81[/tex]
