0.1x^2=4.2x

Solution for 0.1x^2=4.2x equation:

0.1x^2=4.2x

We move all terms to the left:

0.1x^2-(4.2x)=0

We add all the numbers together, and all the variables

0.1x^2-(+4.2x)=0

We get rid of parentheses

0.1x^2-4.2x=0

a = 0.1; b = -4.2; c = 0;
Δ = b2-4ac
Δ = -4.22-4·0.1·0
Δ = 17.64
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{-(-4.2)-\sqrt{17.64}}{2*0.1}=\frac{4.2-\sqrt{17.64}}{0.2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4.2)+\sqrt{17.64}}{2*0.1}=\frac{4.2+\sqrt{17.64}}{0.2}
$