(x+7)(x-1)=-4

Solution for (x+7)(x-1)=-4 equation:

(x+7)(x-1)=-4

We move all terms to the left:

(x+7)(x-1)-(-4)=0

We add all the numbers together, and all the variables

(x+7)(x-1)+4=0

We multiply parentheses ..

(+x^2-1x+7x-7)+4=0

We get rid of parentheses

x^2-1x+7x-7+4=0

We add all the numbers together, and all the variables

x^2+6x-3=0

a = 1; b = 6; c = -3;
Δ = b2-4ac
Δ = 62-4·1·(-3)
Δ = 48
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:

$\sqrt{\Delta}=\sqrt{48}=\sqrt{16*3}=\sqrt{16}*\sqrt{3}=4\sqrt{3}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-4\sqrt{3}}{2*1}=\frac{-6-4\sqrt{3}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+4\sqrt{3}}{2*1}=\frac{-6+4\sqrt{3}}{2}
$