4.9t^2-17.2t=25

Solution for 4.9t^2-17.2t=25 equation:

4.9t^2-17.2t=25

We move all terms to the left:

4.9t^2-17.2t-(25)=0

a = 4.9; b = -17.2; c = -25;
Δ = b2-4ac
Δ = -17.22-4·4.9·(-25)
Δ = 785.84
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{-(-17.2)-\sqrt{785.84}}{2*4.9}=\frac{17.2-\sqrt{785.84}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-17.2)+\sqrt{785.84}}{2*4.9}=\frac{17.2+\sqrt{785.84}}{9.8}
$