4-15x=-9x^2

Solution for 4-15x=-9x^2 equation:

4-15x=-9x^2

We move all terms to the left:

4-15x-(-9x^2)=0

We get rid of parentheses

9x^2-15x+4=0

a = 9; b = -15; c = +4;
Δ = b2-4ac
Δ = -152-4·9·4
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-9}{2*9}=\frac{6}{18}
=1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+9}{2*9}=\frac{24}{18}
=1+1/3
$