0.7136t+0.04t^2=2.8t-3.126

Solution for 0.7136t+0.04t^2=2.8t-3.126 equation:

0.7136t+0.04t^2=2.8t-3.126

We move all terms to the left:

0.7136t+0.04t^2-(2.8t-3.126)=0

We get rid of parentheses

0.04t^2+0.7136t-2.8t+3.126=0

We add all the numbers together, and all the variables

0.04t^2-2.0864t+3.126=0

a = 0.04; b = -2.0864; c = +3.126;
Δ = b2-4ac
Δ = -2.08642-4·0.04·3.126
Δ = 3.85290496
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{-(-2.0864)-\sqrt{3.85290496}}{2*0.04}=\frac{2.0864-\sqrt{3.85290496}}{0.08}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2.0864)+\sqrt{3.85290496}}{2*0.04}=\frac{2.0864+\sqrt{3.85290496}}{0.08}
$