0=x(5-0.4x)

Solution for 0=x(5-0.4x) equation:

0=x(5-0.4x)

We move all terms to the left:

0-(x(5-0.4x))=0

We add all the numbers together, and all the variables

-(x(-0.4x+5))+0=0

We add all the numbers together, and all the variables

-(x(-0.4x+5))=0


We calculate terms in parentheses: -(x(-0.4x+5)), so:

x(-0.4x+5)

We multiply parentheses

0x^2+5x

We add all the numbers together, and all the variables

x^2+5x

Back to the equation:

-(x^2+5x)


We get rid of parentheses

-x^2-5x=0

We add all the numbers together, and all the variables

-1x^2-5x=0

a = -1; b = -5; c = 0;
Δ = b2-4ac
Δ = -52-4·(-1)·0
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-5}{2*-1}=\frac{0}{-2}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+5}{2*-1}=\frac{10}{-2}
=-5
$