-3x(-5x+3)=45

Solution for -3x(-5x+3)=45 equation:

-3x(-5x+3)=45

We move all terms to the left:

-3x(-5x+3)-(45)=0

We multiply parentheses

15x^2-9x-45=0

a = 15; b = -9; c = -45;
Δ = b2-4ac
Δ = -92-4·15·(-45)
Δ = 2781
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:

$\sqrt{\Delta}=\sqrt{2781}=\sqrt{9*309}=\sqrt{9}*\sqrt{309}=3\sqrt{309}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-3\sqrt{309}}{2*15}=\frac{9-3\sqrt{309}}{30}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+3\sqrt{309}}{2*15}=\frac{9+3\sqrt{309}}{30}
$