(8r+7)(r+7)=0

Solution for (8r+7)(r+7)=0 equation:

(8r+7)(r+7)=0

We multiply parentheses ..

(+8r^2+56r+7r+49)=0

We get rid of parentheses

8r^2+56r+7r+49=0

We add all the numbers together, and all the variables

8r^2+63r+49=0

a = 8; b = 63; c = +49;
Δ = b2-4ac
Δ = 632-4·8·49
Δ = 2401
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2401}=49$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(63)-49}{2*8}=\frac{-112}{16}
=-7
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(63)+49}{2*8}=\frac{-14}{16}
=-7/8
$