Answer to Question #97381 in Math for Alexandra

Question

Why wouldn't it be helpful to try and solve the following quadratic equation by taking square roots? 2x^2-2x-9=0

Answer 1

$ax^2+bx+c=0$ is a basic square equation. In our case $a=2; b=-2;c=-9$ .

Solve the quadratic equation using the discriminant.

The discriminant is $D = b^2-4ac=(-2)^2-4*2*(-9)=76$ .

$x_1=\cfrac{-b-\sqrt D}{2a}=\cfrac{2-\sqrt {76}}{4}; x_2=\cfrac{-b+\sqrt D}{2a}=\cfrac{2+\sqrt {76}}{4}$ .

Answer: $x_1=\cfrac{2-\sqrt{76}}{4}; x_2=\cfrac{2+\sqrt{76}}{4}$ .