[a(x):=2^x,b(x):=16^(1/x)];

[is(equal(a(-2),b(-2))),is(equal(a(2),b(2)))];

[[-2,a(-2)],[2,a(2)]];

'limit(a(x),x,0);

[limit(b(x),x,0,minus),limit(b(x),x,0,plus)];