5a^2-55=90

Solution for 5a^2-55=90 equation:

5a^2-55=90

We move all terms to the left:

5a^2-55-(90)=0

We add all the numbers together, and all the variables

5a^2-145=0

a = 5; b = 0; c = -145;
Δ = b2-4ac
Δ = 02-4·5·(-145)
Δ = 2900
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:

$\sqrt{\Delta}=\sqrt{2900}=\sqrt{100*29}=\sqrt{100}*\sqrt{29}=10\sqrt{29}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-10\sqrt{29}}{2*5}=\frac{0-10\sqrt{29}}{10}
=-\frac{10\sqrt{29}}{10}
=-\sqrt{29}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+10\sqrt{29}}{2*5}=\frac{0+10\sqrt{29}}{10}
=\frac{10\sqrt{29}}{10}
=\sqrt{29}
$