SOLUTION: Here's the question-determine whether the equation represents a function, the equation is y^2=x+9. If I isolate y, my equation becomes y=3*sq root of x and it graphs as a function

Algebra ->  Graphs -> SOLUTION: Here's the question-determine whether the equation represents a function, the equation is y^2=x+9. If I isolate y, my equation becomes y=3*sq root of x and it graphs as a function      Log On


   



Question 27030: Here's the question-determine whether the equation represents a function, the equation is y^2=x+9. If I isolate y, my equation becomes y=3*sq root of x and it graphs as a function. The answer in the book says it's not a function because the equation is (y+1)^2=x. ????????
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
I think it's not a function.
y%5E2+=+x+%2B+9
y+=+%2B-sqrt%28x+%2B+9%29
y has two values for every value of x I put in the equation.
For it to be a function, there can be a single value of y for each x.
I can rewrite it as:
y%5E2+-+9+=+x
%28y+%2B+3%29+%2A+%28y+-+3%29+=+x
try y = +4
%284+%2B+3%29+%2A+%284+-+3%29+=+x
7+%2A+1+=+x
+7+=+x
now y = -4
%28-4+%2B+3%29+%2A+%28-4+-+3%29+=+x
%28-1%29+%2A+%28-7%29+=+x
+7+=+x
that's two values of y for one value of x.