(x+7)(8x+-7)=0

Solution for (x+7)(8x+-7)=0 equation:

(x+7)(8x+-7)=0

We add all the numbers together, and all the variables

(x+7)(8x-7)=0

We multiply parentheses ..

(+8x^2-7x+56x-49)=0

We get rid of parentheses

8x^2-7x+56x-49=0

We add all the numbers together, and all the variables

8x^2+49x-49=0

a = 8; b = 49; c = -49;
Δ = b2-4ac
Δ = 492-4·8·(-49)
Δ = 3969
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3969}=63$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(49)-63}{2*8}=\frac{-112}{16}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(49)+63}{2*8}=\frac{14}{16}
=7/8
$