How do you use the vertical line test to show #x^2+y^2=25# is a function?

1 Answer
Jun 4, 2015

The problem is that #x^2+y^2 = 25# is not a function.

Using the vertical line test with the vertical line
#color(white)("XXXX")##x=0#
we see that
#color(white)("XXXX")#there are two solutions for #y# (#+5# and #(-5)#)

That is there are two solution points on the vertical line #x=0#
and therefore
#x^2+y^2= 25# is not a function.