For what values of $y$ does the following equation have no solutions for $x$ ?
$$xy + 5y + 4x + 20=1.$$
Not totally sure about this but....here's my best attempt
xy + 5y + 4x + 20 = 1 rearrange as
xy + 4x = 19 - 5y
x [ y + 4] = [ 19 - 5y ] divide both sides by y + 4
x = [ 19 - 5y ] / [ y + 4 ]
Note that if y = -4 , then x is undefined because we will be dividing the right side by 0
So.....there are no solutions for x if y = -4