2.5^2+x^2=8.1^2

Solution for 2.5^2+x^2=8.1^2 equation:

2.5^2+x^2=8.1^2

We move all terms to the left:

2.5^2+x^2-(8.1^2)=0

We add all the numbers together, and all the variables

x^2-59.36=0

a = 1; b = 0; c = -59.36;
Δ = b2-4ac
Δ = 02-4·1·(-59.36)
Δ = 237.44
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{237.44}}{2*1}=\frac{0-\sqrt{237.44}}{2}
=-\frac{\sqrt{}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{237.44}}{2*1}=\frac{0+\sqrt{237.44}}{2}
=\frac{\sqrt{}}{2}
$