15x+90=5x^2

Solution for 15x+90=5x^2 equation:

15x+90=5x^2

We move all terms to the left:

15x+90-(5x^2)=0

determiningTheFunctionDomain
-5x^2+15x+90=0

a = -5; b = 15; c = +90;
Δ = b2-4ac
Δ = 152-4·(-5)·90
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-45}{2*-5}=\frac{-60}{-10}
=+6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+45}{2*-5}=\frac{30}{-10}
=-3
$