0=(0.3-x)(0.4-x)

Solution for 0=(0.3-x)(0.4-x) equation:

0=(0.3-x)(0.4-x)

We move all terms to the left:

0-((0.3-x)(0.4-x))=0

We add all the numbers together, and all the variables

-((-1x+0.3)(-1x+0.4))+0=0

We add all the numbers together, and all the variables

-((-1x+0.3)(-1x+0.4))=0

We multiply parentheses ..

-((+x^2-0.4x-0.3x+0.12))=0


We calculate terms in parentheses: -((+x^2-0.4x-0.3x+0.12)), so:

(+x^2-0.4x-0.3x+0.12)

We get rid of parentheses

x^2-0.4x-0.3x+0.12

We add all the numbers together, and all the variables

x^2-0.7x+0.12

Back to the equation:

-(x^2-0.7x+0.12)


We get rid of parentheses

-x^2+0.7x-0.12=0

We add all the numbers together, and all the variables

-1x^2+0.7x-0.12=0

a = -1; b = 0.7; c = -0.12;
Δ = b2-4ac
Δ = 0.72-4·(-1)·(-0.12)
Δ = 0.01
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{-(0.7)-\sqrt{0.01}}{2*-1}=\frac{-0.7-\sqrt{0.01}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.7)+\sqrt{0.01}}{2*-1}=\frac{-0.7+\sqrt{0.01}}{-2}
$