30-4x+0,3x^2=28x

Solution for 30-4x+0,3x^2=28x equation:

30-4x+0.3x^2=28x

We move all terms to the left:

30-4x+0.3x^2-(28x)=0

We add all the numbers together, and all the variables

0.3x^2-32x+30=0

a = 0.3; b = -32; c = +30;
Δ = b2-4ac
Δ = -322-4·0.3·30
Δ = 988
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{988}=\sqrt{4*247}=\sqrt{4}*\sqrt{247}=2\sqrt{247}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-32)-2\sqrt{247}}{2*0.3}=\frac{32-2\sqrt{247}}{0.6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-32)+2\sqrt{247}}{2*0.3}=\frac{32+2\sqrt{247}}{0.6}
$