8x^2-9=-1

Solution for 8x^2-9=-1 equation:

8x^2-9=-1

We move all terms to the left:

8x^2-9-(-1)=0

We add all the numbers together, and all the variables

8x^2-8=0

a = 8; b = 0; c = -8;
Δ = b2-4ac
Δ = 02-4·8·(-8)
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-16}{2*8}=\frac{-16}{16}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+16}{2*8}=\frac{16}{16}
=1
$