0.15=x(700+x)

Solution for 0.15=x(700+x) equation:

0.15=x(700+x)

We move all terms to the left:

0.15-(x(700+x))=0

We add all the numbers together, and all the variables

-(x(x+700))+0.15=0


We calculate terms in parentheses: -(x(x+700)), so:

x(x+700)

We multiply parentheses

x^2+700x

Back to the equation:

-(x^2+700x)


We get rid of parentheses

-x^2-700x+0.15=0

We add all the numbers together, and all the variables

-1x^2-700x+0.15=0

a = -1; b = -700; c = +0.15;
Δ = b2-4ac
Δ = -7002-4·(-1)·0.15
Δ = 490000.6
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{-(-700)-\sqrt{490000.6}}{2*-1}=\frac{700-\sqrt{490000.6}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-700)+\sqrt{490000.6}}{2*-1}=\frac{700+\sqrt{490000.6}}{-2}
$