#### Question

# PLEASE HELP ME I TOTALLY SUCK @ MATH?

After being rearranged and simplified, which of the following equations could be solved using the quadratic formula?

Check all that apply.

HERE ARE THE CHOICES

A. 5x2 + 2x - 4 = 2x2

B. 2x2 - 6x - 7 = 2x2

C. 2x2 - 3x + 10 = 2x + 21

D. 5x3 - 3x + 10 = 2x2

#### Answer

Only quadratic equations can be solved by the quadratic formula. Since D is a cubic equation, it is out. The quadratic term cancels out of B so it is in fact a linear equation and it is out. Both A and C remain quadratic when all terms are moved to one side and combined, so the answer is A and C.

quadratic formula states that given ax^2 + bx + c = 0

x= (-b +/- √(b^2-4*a*c))/(2*a)

so need equations in form ax^2 + bx + c = 0

A. 5x^2 - 2x^2 + 2x - 4 = 0 (subtracting 2x^2 from both sides)

3x^2 +2x - 4 = 0, so the quadratic formula applies

B 2x^2 -2x^2 - 6x -7 = 0 (subtracting 2x^2 from both sides)

-6x - 7 = 0 so cannot be solved with quadratic formula

C 2x^2 - 3x + 10 - 2x - 21 = 0 (subtracting 2x + 21 from both sides)

2x^2 -5x -11 = 0, so quadratic formula applies

D 5x^3 -2x^2 - 3x - 10 = 0 , so cannoth be solved with formula (since x^3 term is present)