Answer:
The form ax2 + bx + c = 0 is called standard form of a quadratic equation. Before solving a quadratic equation using the Quadratic Formula, it's vital that you be sure the equation is in this form.
Step-by-step explanation:
D
the last one
5ab-ab+9a-7a
ab(5-1)+a(9-7)
4ab+2a
a(4b+2)
