-140=-2(8r+6)r=

Solution for -140=-2(8r+6)r= equation:

-140=-2(8r+6)r=

We move all terms to the left:

-140-(-2(8r+6)r)=0


We calculate terms in parentheses: -(-2(8r+6)r), so:

-2(8r+6)r

We multiply parentheses

-16r^2-12r

Back to the equation:

-(-16r^2-12r)


We get rid of parentheses

16r^2+12r-140=0

a = 16; b = 12; c = -140;
Δ = b2-4ac
Δ = 122-4·16·(-140)
Δ = 9104
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{9104}=\sqrt{16*569}=\sqrt{16}*\sqrt{569}=4\sqrt{569}$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-4\sqrt{569}}{2*16}=\frac{-12-4\sqrt{569}}{32}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+4\sqrt{569}}{2*16}=\frac{-12+4\sqrt{569}}{32}
$