-2(m-5)4m=15

Solution for -2(m-5)4m=15 equation:

-2(m-5)4m=15

We move all terms to the left:

-2(m-5)4m-(15)=0

We multiply parentheses

-8m^2+40m-15=0

a = -8; b = 40; c = -15;
Δ = b2-4ac
Δ = 402-4·(-8)·(-15)
Δ = 1120
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1120}=\sqrt{16*70}=\sqrt{16}*\sqrt{70}=4\sqrt{70}$
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-4\sqrt{70}}{2*-8}=\frac{-40-4\sqrt{70}}{-16}
$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+4\sqrt{70}}{2*-8}=\frac{-40+4\sqrt{70}}{-16}
$