# algebraic question

• Jul 28th 2005, 12:24 AM
futsalfred
I have also another algebric quesion to ask. I found this equation EXTREMELY EASY, but many of my friends in the class don't know the ans. not even the smartest math guy in the class, he has a deformed head, he says that he studies too much and it goes weird. so heres the quesrtion.

if x+z=y,
and x+9(7-7)=y,
what is z+x+y?
I ansered x+y.
(oh yeah, this has nothing to do with the previous question.)
is this question really that difficult? and did i get the answer correct?? w the? :eek:
• Jul 28th 2005, 01:05 AM
ticbol
Yes, x+y+z = x+y. ----one correct answer.

Also,
x+y+z = 2x ----another correct answer.
x+y+z = 2y ----still another correct answer.

Is the question really that difficult?
No.
In fact, it is really that easy.
• Jul 28th 2005, 01:07 AM
futsalfred
Quote:

Originally Posted by ticbol
Yes, x+y+z = x+y. ----one correct answer.

Also,
x+y+z = 2x ----another correct answer.
x+y+z = 2y ----still another correct answer.

Is the question really that difficult?
No.
In fact, it is really that easy.

how did you get 2x abd 2y as answers?
• Jul 28th 2005, 02:21 AM
ticbol
You figured correctly that z=0. That is why you got x+y+z = x+y.

So if z=0,
x+z=y,
x+0 = y
x = y ------***

Then,
x+y+z
= x +y +0
= x +y -----(1)

But x=y,
So, substitute that into (1),
= y +y
= 2y

Also, since x=y, then y=x.
So, substitute that into (1),
= x +x
= 2x

-------------------------
But why is z equal to zero?
Did you guess that, or you found it?

Anyway, this is why z=0.

if x+z=y,
and x+9(7-7)=y,
what is z+x+y?

x +9(7-7) = y
x +9(0) = y
x +0 = y
x = y -----***
Substitute that into "if x+z=y",
x +z = y
y +z = y
z = y -y
z = 0

That is why.
• Jul 30th 2005, 10:07 PM
futsalfred
okay
okay, thanks for your time :)