(10y+15)(0,3-1,2y)=0

Solution for (10y+15)(0,3-1,2y)=0 equation:

(10y+15)(0.3-1.2y)=0

We add all the numbers together, and all the variables

(10y+15)(-1.2y+0.3)=0

We multiply parentheses ..

(-10y^2+3y-15y+4.5)=0

We get rid of parentheses

-10y^2+3y-15y+4.5=0

We add all the numbers together, and all the variables

-10y^2-12y+4.5=0

a = -10; b = -12; c = +4.5;
Δ = b2-4ac
Δ = -122-4·(-10)·4.5
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-18}{2*-10}=\frac{-6}{-20}
=3/10
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+18}{2*-10}=\frac{30}{-20}
=-1+1/2
$