-x(x+7)=-2(x+10)

Solution for -x(x+7)=-2(x+10) equation:

-x(x+7)=-2(x+10)

We move all terms to the left:

-x(x+7)-(-2(x+10))=0

We multiply parentheses

-x^2-7x-(-2(x+10))=0


We calculate terms in parentheses: -(-2(x+10)), so:

-2(x+10)

We multiply parentheses

-2x-20

Back to the equation:

-(-2x-20)


We add all the numbers together, and all the variables

-1x^2-7x-(-2x-20)=0

We get rid of parentheses

-1x^2-7x+2x+20=0

We add all the numbers together, and all the variables

-1x^2-5x+20=0

a = -1; b = -5; c = +20;
Δ = b2-4ac
Δ = -52-4·(-1)·20
Δ = 105
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{-(-5)-\sqrt{105}}{2*-1}=\frac{5-\sqrt{105}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+\sqrt{105}}{2*-1}=\frac{5+\sqrt{105}}{-2}
$