(5y-7)*(2y-0,4)=0

Solution for (5y-7)*(2y-0,4)=0 equation:

(5y-7)(2y-0.4)=0

We multiply parentheses ..

(+10y^2-2y-14y+2.8)=0

We get rid of parentheses

10y^2-2y-14y+2.8=0

We add all the numbers together, and all the variables

10y^2-16y+2.8=0

a = 10; b = -16; c = +2.8;
Δ = b2-4ac
Δ = -162-4·10·2.8
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-12}{2*10}=\frac{4}{20}
=1/5
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+12}{2*10}=\frac{28}{20}
=1+2/5
$