9=(x^2-1)

Solution for 9=(x^2-1) equation:

9=(x^2-1)

We move all terms to the left:

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


We calculate terms in parentheses: -((x^2-1)), so:

(x^2-1)

We get rid of parentheses

x^2-1

Back to the equation:

-(x^2-1)


We get rid of parentheses

-x^2+1+9=0

We add all the numbers together, and all the variables

-1x^2+10=0

a = -1; b = 0; c = +10;
Δ = b2-4ac
Δ = 02-4·(-1)·10
Δ = 40
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{40}=\sqrt{4*10}=\sqrt{4}*\sqrt{10}=2\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{10}}{2*-1}=\frac{0-2\sqrt{10}}{-2}
=-\frac{2\sqrt{10}}{-2}
=-\frac{\sqrt{10}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{10}}{2*-1}=\frac{0+2\sqrt{10}}{-2}
=\frac{2\sqrt{10}}{-2}
=\frac{\sqrt{10}}{-1}
$