0.15=x(x+0.2)

Solution for 0.15=x(x+0.2) equation:

0.15=x(x+0.2)

We move all terms to the left:

0.15-(x(x+0.2))=0


We calculate terms in parentheses: -(x(x+0.2)), so:

x(x+0.2)

We multiply parentheses

x^2+0.2x

Back to the equation:

-(x^2+0.2x)


We get rid of parentheses

-x^2-0.2x+0.15=0

We add all the numbers together, and all the variables

-1x^2-0.2x+0.15=0

a = -1; b = -0.2; c = +0.15;
Δ = b2-4ac
Δ = -0.22-4·(-1)·0.15
Δ = 0.64
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{-(-0.2)-\sqrt{0.64}}{2*-1}=\frac{0.2-\sqrt{0.64}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.2)+\sqrt{0.64}}{2*-1}=\frac{0.2+\sqrt{0.64}}{-2}
$