document.write( "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. ???????? \n" ); document.write( "

Algebra.Com's Answer #14691 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
I think it's not a function.
\n" ); document.write( " $\"y%5E2+=+x+%2B+9\"$
\n" ); document.write( " $\"y+=+%2B-sqrt%28x+%2B+9%29\"$
\n" ); document.write( "y has two values for every value of x I put in the equation.
\n" ); document.write( "For it to be a function, there can be a single value of y for each x.
\n" ); document.write( "I can rewrite it as:
\n" ); document.write( " $\"y%5E2+-+9+=+x\"$
\n" ); document.write( " $\"%28y+%2B+3%29+%2A+%28y+-+3%29+=+x\"$
\n" ); document.write( "try y = +4
\n" ); document.write( " $\"%284+%2B+3%29+%2A+%284+-+3%29+=+x\"$
\n" ); document.write( " $\"7+%2A+1+=+x\"$
\n" ); document.write( " $\"+7+=+x\"$
\n" ); document.write( "now y = -4
\n" ); document.write( " $\"%28-4+%2B+3%29+%2A+%28-4+-+3%29+=+x\"$
\n" ); document.write( " $\"%28-1%29+%2A+%28-7%29+=+x\"$
\n" ); document.write( " $\"+7+=+x\"$
\n" ); document.write( "that's two values of y for one value of x. \n" ); document.write( "

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