where did i go wrong?

Question

X=Y
X^2=XY
Y^2=XY
(X+Y)(X-Y)= Y(X-Y)
devide by (X-Y)
X+Y=Y
if X=1
then Y=1
so 1+1=1?

Answer 1

you divide by X-Y, but X-Y =0 and you cant divide by 0 in maths-its not defined (not allowed basically!)

Answer 2

Where did i go wrong?
X=Y
X^2=XY
Y^2=XY
(X+Y)(X-Y)= Y(X-Y)
devide by (X-Y) ....YOU MISSPELLED DIVIDE That's where you went wrong.
X+Y=Y
if X=1
then Y=1
so 1+1=1?

Answer 3

step 3 to 4

Answer 4

In step 5 you divided by x-y which is 0
Division by zero is not permitted.
This is such a well known puzzle that I am surprized it still makes the rounds.

Answer 5

well...put in 1 at the 3rd line...you have (2)(0)=1(0)
so 0=0... you really cant continue, and if you say, yeah but we are gonna divide by x-y to get rid of that issue, now your dividing by zero...and you cant do that

hope that helped
matttlocke

Answer 6

I think this will only work for X=0 & Y=0, but I'm not that good in math, maybe I'm overlooking something!

Answer 7

(X+Y)(X-Y)= Y(X-Y)
this implies that Y = X+Y, and that can only be true if X and Y both equal 0

also, If X = Y, then X-Y= 0

So this statement comes out to be 0=0

plus you can't divide by (X-Y) because that is dividing by 0

Answer 8

Line five (divide by (X-Y)) is invalid because X-Y=0.

You cannot divide by zero.

Answer 9

The fourth line doesn't equal to the previous line. It is wrong.
(X+Y)(X-Y)= Y(X-Y)

equals

x^2-y^2 = xy-y^2

add y^2

x^2 = xy is wrong.

Answer 10

if x = y , then x^2 = y^2 ... no ?
unless, and only unless the book statest that Y^2=XY and X^2=XY
Anyways!
(X+Y)(X-Y)= X (Y-Y) NOT Y(X-Y)