70=25x+4.9x^2

Solution for 70=25x+4.9x^2 equation:

70=25x+4.9x^2

We move all terms to the left:

70-(25x+4.9x^2)=0

We get rid of parentheses

-4.9x^2-25x+70=0

a = -4.9; b = -25; c = +70;
Δ = b2-4ac
Δ = -252-4·(-4.9)·70
Δ = 1997
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{-(-25)-\sqrt{1997}}{2*-4.9}=\frac{25-\sqrt{1997}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-25)+\sqrt{1997}}{2*-4.9}=\frac{25+\sqrt{1997}}{-9.8}
$