Question

Which of the following are solutions to 2x2 – 8x - 90? Select all that apply.

Answer 1

Answer:

x=-5, x=9

Step-by-step explanation:

we know that

The formula to solve a quadratic equation of the form

$ax^{2} +bx+c=0$

is equal to

$x=\frac{-b\pm\sqrt{b^{2}-4ac}} {2a}$

in this problem we have

$2x^{2} -8x-90$  

equate to zero

$2x^{2} -8x-90=0$  

so

$2=-1\\b=-8\\c=-90$

substitute in the formula

$x=\frac{-(-8)\pm\sqrt{-8^{2}-4(2)(-90)}} {2(2)}$

$x=\frac{8\pm\sqrt{784}} {4}$

$x=\frac{8\pm28} {4}$

$x=\frac{8+28} {4}=9$

$x=\frac{8-28} {4}=-5$

therefore

The solutions are x=-5, x=9