-0.2=-4.9x^2+21x

Solution for -0.2=-4.9x^2+21x equation:

-0.2=-4.9x^2+21x

We move all terms to the left:

-0.2-(-4.9x^2+21x)=0

We get rid of parentheses

4.9x^2-21x-0.2=0

a = 4.9; b = -21; c = -0.2;
Δ = b2-4ac
Δ = -212-4·4.9·(-0.2)
Δ = 444.92
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{-(-21)-\sqrt{444.92}}{2*4.9}=\frac{21-\sqrt{444.92}}{9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+\sqrt{444.92}}{2*4.9}=\frac{21+\sqrt{444.92}}{9.8}
$