30*x^2+90*x-73.6=0

Solution for 30*x^2+90*x-73.6=0 equation:

30x^2+90x-73.6=0

a = 30; b = 90; c = -73.6;
Δ = b2-4ac
Δ = 902-4·30·(-73.6)
Δ = 16932
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{16932}=\sqrt{4*4233}=\sqrt{4}*\sqrt{4233}=2\sqrt{4233}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(90)-2\sqrt{4233}}{2*30}=\frac{-90-2\sqrt{4233}}{60}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(90)+2\sqrt{4233}}{2*30}=\frac{-90+2\sqrt{4233}}{60}
$