3x(3x-4)=+45

Solution for 3x(3x-4)=+45 equation:

3x(3x-4)=+45

We move all terms to the left:

3x(3x-4)-(+45)=0

We add all the numbers together, and all the variables

3x(3x-4)-45=0

We multiply parentheses

9x^2-12x-45=0

a = 9; b = -12; c = -45;
Δ = b2-4ac
Δ = -122-4·9·(-45)
Δ = 1764
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1764}=42$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-42}{2*9}=\frac{-30}{18}
=-1+2/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+42}{2*9}=\frac{54}{18}
=3
$