6.15x+6.15x(6.15x)=45

Solution for 6.15x+6.15x(6.15x)=45 equation:

6.15x+6.15x(6.15x)=45

We move all terms to the left:

6.15x+6.15x(6.15x)-(45)=0

We add all the numbers together, and all the variables

6.15x+6.15x(+6.15x)-45=0

We multiply parentheses

36x^2+6.15x-45=0

a = 36; b = 6.15; c = -45;
Δ = b2-4ac
Δ = 6.152-4·36·(-45)
Δ = 6517.8225
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{-(6.15)-\sqrt{6517.8225}}{2*36}=\frac{-6.15-\sqrt{6517.8225}}{72}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6.15)+\sqrt{6517.8225}}{2*36}=\frac{-6.15+\sqrt{6517.8225}}{72}
$