5x*4x=15+9x

Solution for 5x*4x=15+9x equation:

5x*4x=15+9x

We move all terms to the left:

5x*4x-(15+9x)=0

We add all the numbers together, and all the variables

5x*4x-(9x+15)=0

Wy multiply elements

20x^2-(9x+15)=0

We get rid of parentheses

20x^2-9x-15=0

a = 20; b = -9; c = -15;
Δ = b2-4ac
Δ = -92-4·20·(-15)
Δ = 1281
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-\sqrt{1281}}{2*20}=\frac{9-\sqrt{1281}}{40}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+\sqrt{1281}}{2*20}=\frac{9+\sqrt{1281}}{40}
$