Question

Which quadratic equation crosses the x-axis at 4 and -9?

A. y=x^2-5x-36
B. y=x^2+5x+36
C. y=x^2+5x-36
D. y=x^2-5x+36

Answer 1

if it crosses at r1,r2 then it factors to f(x)=(x-r1)(x-r2)
crosses at 4 and -9
factors to f(x)=(x-4)(x-(-9))=(x-4)(x+9)=x²+5x-36


answer is C