(2r-2)(-r-7)=0

Solution for (2r-2)(-r-7)=0 equation:

(2r-2)(-r-7)=0

We add all the numbers together, and all the variables

(2r-2)(-1r-7)=0

We multiply parentheses ..

(-2r^2-14r+2r+14)=0

We get rid of parentheses

-2r^2-14r+2r+14=0

We add all the numbers together, and all the variables

-2r^2-12r+14=0

a = -2; b = -12; c = +14;
Δ = b2-4ac
Δ = -122-4·(-2)·14
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-16}{2*-2}=\frac{-4}{-4}
=1
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+16}{2*-2}=\frac{28}{-4}
=-7
$