T(m)=-5m2+40m

Solution for T(m)=-5m2+40m equation:

(T)=-5T^2+40T

We move all terms to the left:

(T)-(-5T^2+40T)=0

We get rid of parentheses

5T^2-40T+T=0

We add all the numbers together, and all the variables

5T^2-39T=0

a = 5; b = -39; c = 0;
Δ = b2-4ac
Δ = -392-4·5·0
Δ = 1521
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$T_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$T_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1521}=39$
$T_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-39)-39}{2*5}=\frac{0}{10}
=0
$
$T_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-39)+39}{2*5}=\frac{78}{10}
=7+4/5
$