15=9(3x-x)x=

Solution for 15=9(3x-x)x= equation:

15=9(3x-x)x=

We move all terms to the left:

15-(9(3x-x)x)=0

We add all the numbers together, and all the variables

-(9(+2x)x)+15=0


We calculate terms in parentheses: -(9(+2x)x), so:

9(+2x)x

We multiply parentheses

18x^2

Back to the equation:

-(18x^2)


a = -18; b = 0; c = +15;
Δ = b2-4ac
Δ = 02-4·(-18)·15
Δ = 1080
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:

$\sqrt{\Delta}=\sqrt{1080}=\sqrt{36*30}=\sqrt{36}*\sqrt{30}=6\sqrt{30}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-6\sqrt{30}}{2*-18}=\frac{0-6\sqrt{30}}{-36}
=-\frac{6\sqrt{30}}{-36}
=-\frac{\sqrt{30}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+6\sqrt{30}}{2*-18}=\frac{0+6\sqrt{30}}{-36}
=\frac{6\sqrt{30}}{-36}
=\frac{\sqrt{30}}{-6}
$