-7x(x+3)=-35

Solution for -7x(x+3)=-35 equation:

-7x(x+3)=-35

We move all terms to the left:

-7x(x+3)-(-35)=0

We add all the numbers together, and all the variables

-7x(x+3)+35=0

We multiply parentheses

-7x^2-21x+35=0

a = -7; b = -21; c = +35;
Δ = b2-4ac
Δ = -212-4·(-7)·35
Δ = 1421
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1421}=\sqrt{49*29}=\sqrt{49}*\sqrt{29}=7\sqrt{29}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-7\sqrt{29}}{2*-7}=\frac{21-7\sqrt{29}}{-14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+7\sqrt{29}}{2*-7}=\frac{21+7\sqrt{29}}{-14}
$