Question 1086079
y=-x, f(x)=-x
change x to -x; f(-x)=-(-x)=x
not symmetric with regards to the y-axis. Not an even function
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f(x)=-x
-f(x)==x.  Not an odd function
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Graph it and turn the graph upside down.  It looks the same.  Symmetrical about the origin.
Or, replace y with -y and x with -x, and we have -y=x, which is the function.
{{{graph(300,300,-10,10,-10,10,-x)}}}