SOLUTION: (x-8/x+5)/(x-9/x+4) why cant -5, 9, and -4 not allowable replacements for the variable x.

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: (x-8/x+5)/(x-9/x+4) why cant -5, 9, and -4 not allowable replacements for the variable x.       Log On


   

Question 149248: (x-8/x+5)/(x-9/x+4) why cant -5, 9, and -4 not allowable replacements for the variable x.


Found 2 solutions by nerdybill, ankor@dixie-net.com:
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
If a denominator is zero, the term is "undefined".
.
(x-8/x+5)/(x-9/x+4)
.
if x=-5, we would have:
(x-8/x+5)/(x-9/x+4)
(x-8/0+5)/(x-9/x+4)
(x-8/0)/(x-9/x+4)
Notice the numerator (x-8)/0 -- this is undefined
.
if x=9, we would have:
(x-8/x+5)/(x-9/x+4)
(x-8/x+5)/(0-9/x+4)
(x-8/x+5)/(0/x+4)
(x-8/x+5)/(0)
Again we have a denominator equal to zero -- undefined
.
if x = -4, we would have:
(x-8/x+5)/(x-9/x+4)
(x-8/x+5)/(x-9/-4+4)
(x-8/x+5)/(x-9/0)
Notice the denominator (x-9)/0 -- this is undefined

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
All these values would put 0 as the denominator, a big no-no in algebra