100=1.3x^2

Solution for 100=1.3x^2 equation:

100=1.3x^2

We move all terms to the left:

100-(1.3x^2)=0

We get rid of parentheses

-1.3x^2+100=0

a = -1.3; b = 0; c = +100;
Δ = b2-4ac
Δ = 02-4·(-1.3)·100
Δ = 520
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:

$\sqrt{\Delta}=\sqrt{520}=\sqrt{4*130}=\sqrt{4}*\sqrt{130}=2\sqrt{130}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{130}}{2*-1.3}=\frac{0-2\sqrt{130}}{-2.6}
=-\frac{2\sqrt{130}}{-2.6}
=-\frac{\sqrt{130}}{-1.3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{130}}{2*-1.3}=\frac{0+2\sqrt{130}}{-2.6}
=\frac{2\sqrt{130}}{-2.6}
=\frac{\sqrt{130}}{-1.3}
$