0=-4.7t+4.9t^2

Solution for 0=-4.7t+4.9t^2 equation:

0=-4.7t+4.9t^2

We move all terms to the left:

0-(-4.7t+4.9t^2)=0

We add all the numbers together, and all the variables

-(-4.7t+4.9t^2)=0

We get rid of parentheses

-4.9t^2+4.7t=0

a = -4.9; b = 4.7; c = 0;
Δ = b2-4ac
Δ = 4.72-4·(-4.9)·0
Δ = 22.09
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{-(4.7)-\sqrt{22.09}}{2*-4.9}=\frac{-4.7-\sqrt{22.09}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4.7)+\sqrt{22.09}}{2*-4.9}=\frac{-4.7+\sqrt{22.09}}{-9.8}
$