For what values of y does the following equation have no solutions for x?
xy+5y+4x+20=1
Clearly we'll have an equation of the form $ax+b=ax+c$. So $y=-4$, so $-4x+4x=1$, impossible.
Ans: $\boxed{-4}$.
Or, you could factor:
\((x+5)(y+4)=1\)
When y = -4, the left-hand side will always equal zero, so \(\boxed{y=-4}\) is the solution.
+600 
