Question

Which value of b would make x²+bx-30 factorable?
A. -31
B. -17
C. 11
D. 13

Answer 1

I think the answer is. D 14

Answer 2

D. 13

Explanation:

well since it's a quadratic equation, it can be written in the form of ax²+bx+c=0. So we have a=1, b=b and c= -30. Also the roots are given by the equation-

x= -b±
`\sqrt{b^(2)-4ac}` /2a. So all I did was put the number from the choices which would satisfy the sqrt part and that turned out to be 13 since
`\sqrt{13^(2)-4*1*(-30)` =
`√(289)` = 17. So b=13.