In case of parallel lines

Where a1, b1 and c1 are the constants of the first equation and a2, b2 and c2 are the constants of the second equation
From first equation (5x+10y+4 = 0)
a1 = 5
b1 = 10
c1 = 4
So now what we want to do is to divide 5 by a number and 10 by another number to get the same result at the end
I'll divide 5 by 1 and 10 by 2 to get the same number 5
5/1 = 10/2
Then I'll divide 4 by any number to get a result other than 5
Let's say 4 (or any other number it can be positive as well as negative)
So
a2 = 1
b2 = 2
c2 = 4
Then now the last step is to write the equation using these constants
x + 2y +4 =0
x+2y= - 4
Therefore this equation is parallel to 5x+10y = - 4