T=-0.1t^2+2.8t+2

Solution for T=-0.1t^2+2.8t+2 equation:

=-0.1T^2+2.8T+2

We move all terms to the left:

-(-0.1T^2+2.8T+2)=0

We get rid of parentheses

0.1T^2-2.8T-2=0

a = 0.1; b = -2.8; c = -2;
Δ = b2-4ac
Δ = -2.82-4·0.1·(-2)
Δ = 8.64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$T_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$T_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$T_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2.8)-\sqrt{8.64}}{2*0.1}=\frac{2.8-\sqrt{8.64}}{0.2}
$
$T_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2.8)+\sqrt{8.64}}{2*0.1}=\frac{2.8+\sqrt{8.64}}{0.2}
$