92=2+10c2

Solution for 92=2+10c2 equation:

92=2+10c^2

We move all terms to the left:

92-(2+10c^2)=0

We get rid of parentheses

-10c^2-2+92=0

We add all the numbers together, and all the variables

-10c^2+90=0

a = -10; b = 0; c = +90;
Δ = b2-4ac
Δ = 02-4·(-10)·90
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-60}{2*-10}=\frac{-60}{-20}
=+3
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+60}{2*-10}=\frac{60}{-20}
=-3
$