0.75t=-4.9t^2+20t

Solution for 0.75t=-4.9t^2+20t equation:

0.75t=-4.9t^2+20t

We move all terms to the left:

0.75t-(-4.9t^2+20t)=0

We get rid of parentheses

4.9t^2-20t+0.75t=0

We add all the numbers together, and all the variables

4.9t^2-19.25t=0

a = 4.9; b = -19.25; c = 0;
Δ = b2-4ac
Δ = -19.252-4·4.9·0
Δ = 370.5625
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{-(-19.25)-\sqrt{370.5625}}{2*4.9}=\frac{19.25-\sqrt{370.5625}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-19.25)+\sqrt{370.5625}}{2*4.9}=\frac{19.25+\sqrt{370.5625}}{9.8}
$