21.2=-0.3x^2-5.4x+38

Solution for 21.2=-0.3x^2-5.4x+38 equation:

21.2=-0.3x^2-5.4x+38

We move all terms to the left:

21.2-(-0.3x^2-5.4x+38)=0

We get rid of parentheses

0.3x^2+5.4x-38+21.2=0

We add all the numbers together, and all the variables

0.3x^2+5.4x-16.8=0

a = 0.3; b = 5.4; c = -16.8;
Δ = b2-4ac
Δ = 5.42-4·0.3·(-16.8)
Δ = 49.32
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{-(5.4)-\sqrt{49.32}}{2*0.3}=\frac{-5.4-\sqrt{49.32}}{0.6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5.4)+\sqrt{49.32}}{2*0.3}=\frac{-5.4+\sqrt{49.32}}{0.6}
$