Question

The roots of the equation x^2+bx+c =0 are -4 and 2. Find c using the quadratic formula

Answer 1

Answer:

Step-by-step explanation:

Hello,

c= -4 * 2 = -8 as

$x^2+bx+c=(x+4)(x-2)=x^2+2x-8$

with the quadratic formula

$x_1=\dfrac{-b+\sqrt{b^2-4ac}}{2a}\\\\x_2=\dfrac{-b-\sqrt{b^2-4ac}}{2a}$

And

$x_1x_2=\dfrac{b^2-b^2+4ac}{4a^2}=\dfrac{c}{a}$

thanks