-7x2+13=0

Solution for -7x2+13=0 equation:

-7x^2+13=0

a = -7; b = 0; c = +13;
Δ = b2-4ac
Δ = 02-4·(-7)·13
Δ = 364
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:

$\sqrt{\Delta}=\sqrt{364}=\sqrt{4*91}=\sqrt{4}*\sqrt{91}=2\sqrt{91}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{91}}{2*-7}=\frac{0-2\sqrt{91}}{-14}
=-\frac{2\sqrt{91}}{-14}
=-\frac{\sqrt{91}}{-7}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{91}}{2*-7}=\frac{0+2\sqrt{91}}{-14}
=\frac{2\sqrt{91}}{-14}
=\frac{\sqrt{91}}{-7}
$