Question

How do you evaluate `sqrt(b^2-4ac)` for a=2, b=-4, c=-6?

Answer 1

The discriminant `D=(-4)^2-4*2*(-6)`

Explanation:

`D=16-(-48)=16+48=64` This is `>0`
so there will be two solutions to the equation `2x^2-4x-6=0`

The square root `sqrtD=sqrt64=8`

The two solutions being:

`x_(1,2)=(-b+-sqrtD)/(2a)=(+4+-8)/4=1+-2`

`->x=+3orx=-1`