(x)=-4x^2+21.3x

Solution for (x)=-4x^2+21.3x equation:

(x)=-4x^2+21.3x

We move all terms to the left:

(x)-(-4x^2+21.3x)=0

We get rid of parentheses

4x^2-21.3x+x=0

We add all the numbers together, and all the variables

4x^2-20.3x=0

a = 4; b = -20.3; c = 0;
Δ = b2-4ac
Δ = -20.32-4·4·0
Δ = 412.09
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{-(-20.3)-\sqrt{412.09}}{2*4}=\frac{20.3-\sqrt{412.09}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20.3)+\sqrt{412.09}}{2*4}=\frac{20.3+\sqrt{412.09}}{8}
$