25=4.9x^2-10x

Solution for 25=4.9x^2-10x equation:

25=4.9x^2-10x

We move all terms to the left:

25-(4.9x^2-10x)=0

We get rid of parentheses

-4.9x^2+10x+25=0

a = -4.9; b = 10; c = +25;
Δ = b2-4ac
Δ = 102-4·(-4.9)·25
Δ = 590
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-\sqrt{590}}{2*-4.9}=\frac{-10-\sqrt{590}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+\sqrt{590}}{2*-4.9}=\frac{-10+\sqrt{590}}{-9.8}
$