3a^2+60a-900=0

Solution for 3a^2+60a-900=0 equation:

3a^2+60a-900=0

a = 3; b = 60; c = -900;
Δ = b2-4ac
Δ = 602-4·3·(-900)
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-120}{2*3}=\frac{-180}{6}
=-30
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+120}{2*3}=\frac{60}{6}
=10
$