Question 72881
X^2-4X=5
X^2-4X-5=0
(X-5)(X+1)=0 [IF YOU MULTIPLY THESE TWO TERMS YOU GET (X^2-5X+X-5) NOW COMBINING LIKE TERMS YOU GET X^2-4X-5. THE 4X DIDNT DISAPPEAR IT JUST GOT FACTORED INTO (-5X & X WHICH = 4X)  
X-5=0
X=5 ANSWER.
X+1=0
X=-1 ANSWER.