Question 383534
{{{ y = x^2 / (x^2-16)}}}

Domain : possible value for x. If x=+4 or -4, there is a division by zero, all other value are possible, hence Dom(y(x))=R-{+4,-4}

Range : all values that y reaches, seek for the inverse : 
 
y*x^2-16y = x^2
x^2(1-y)=-16y
 
x^2=16y/(y-1)
 
thus 1 is not allowed for y, more over y/(y-1) has to be positive : 
 
cases : y>0 and y-1>0<=>y>1, 
 
y<0 and y-1<0<=>y<1, hence y<0
 
so the range of y is : Range(y(x))=]-oo;0]U[1,+oo[

Graph : 

{{{graph( 600, 200, -10, 10, -10, 10, x^2/(x^2-16), 1) }}}