18.8=15+x*x

Solution for 18.8=15+x*x equation:

18.8=15+x*x

We move all terms to the left:

18.8-(15+x*x)=0

We add all the numbers together, and all the variables

-(x*x+15)+18.8=0

We get rid of parentheses

-x*x-15+18.8=0

We add all the numbers together, and all the variables

-x*x+3.8=0

Wy multiply elements

-1x^2+3.8=0

a = -1; b = 0; c = +3.8;
Δ = b2-4ac
Δ = 02-4·(-1)·3.8
Δ = 15.2
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-\sqrt{15.2}}{2*-1}=\frac{0-\sqrt{15.2}}{-2}
=-\frac{\sqrt{}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{15.2}}{2*-1}=\frac{0+\sqrt{15.2}}{-2}
=\frac{\sqrt{}}{-2}
$