a2-18a=10

Solution for a2-18a=10 equation:

a2-18a=10

We move all terms to the left:

a2-18a-(10)=0

We add all the numbers together, and all the variables

a^2-18a-10=0

a = 1; b = -18; c = -10;
Δ = b2-4ac
Δ = -182-4·1·(-10)
Δ = 364
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{364}=\sqrt{4*91}=\sqrt{4}*\sqrt{91}=2\sqrt{91}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-2\sqrt{91}}{2*1}=\frac{18-2\sqrt{91}}{2}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+2\sqrt{91}}{2*1}=\frac{18+2\sqrt{91}}{2}
$