5x^2-3-15=0

Solution for 5x^2-3-15=0 equation:

5x^2-3-15=0

We add all the numbers together, and all the variables

5x^2-18=0

a = 5; b = 0; c = -18;
Δ = b2-4ac
Δ = 02-4·5·(-18)
Δ = 360
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:

$\sqrt{\Delta}=\sqrt{360}=\sqrt{36*10}=\sqrt{36}*\sqrt{10}=6\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-6\sqrt{10}}{2*5}=\frac{0-6\sqrt{10}}{10}
=-\frac{6\sqrt{10}}{10}
=-\frac{3\sqrt{10}}{5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+6\sqrt{10}}{2*5}=\frac{0+6\sqrt{10}}{10}
=\frac{6\sqrt{10}}{10}
=\frac{3\sqrt{10}}{5}
$