Posted by krista on Tuesday, April 13, 2010 at 9:35pm.
show that k(x)= (5x^3) + (5/x^3)  x (1/x)

math191  krista, Tuesday, April 13, 2010 at 9:36pm
^ sorry didn't finish: show that k(x)= k(1/x)

math191  Reiny, Tuesday, April 13, 2010 at 9:39pm
let me rewrite k(x)
k(x) = 5(x^3) + 5(1/x^3)  x/1  1/x
it should be intuitively obvious that
k(x) = k(1/x) 
math191  krista, Tuesday, April 13, 2010 at 9:41pm
yea i realize that but the question says "show" that they equal each other. im thinking possibly by some sort of identity or something.

math191  Reiny, Tuesday, April 13, 2010 at 9:45pm
sub 1/x for x
k(1/x) = 5(1/x^3) + 5/(1/x^3)  1/x  1/(1/x)
= 5/x^3 + 5x^3  1/x  x
= the original k(x) , just the order of writing down the terms has changed. 
math191  krista, Tuesday, April 13, 2010 at 9:50pm
ohh i see duh!! lol thanks =)