How can you use y=43 + 5x to solve 78=43 + 5x?

Ineed with number 17 i don’t get it at alll

Its due ! write an equation in which the quadratic expression 2x^2-2x 12 equals 0. show the expression in factored form and explain what your solutions mean for the equation. show your work.

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)