(-1x-0.3)(0.4x-20)=0

Solution for (-1x-0.3)(0.4x-20)=0 equation:

(-1x-0.3)(0.4x-20)=0

We multiply parentheses ..

(+0x^2+20x-0x+6)=0

We get rid of parentheses

0x^2+20x-0x+6=0

We add all the numbers together, and all the variables

x^2+19x+6=0

a = 1; b = 19; c = +6;
Δ = b2-4ac
Δ = 192-4·1·6
Δ = 337
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{-(19)-\sqrt{337}}{2*1}=\frac{-19-\sqrt{337}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(19)+\sqrt{337}}{2*1}=\frac{-19+\sqrt{337}}{2}
$