calculus
posted by donna .
y=5/x3
find the zeros,relative min and max.the max and min
find the intervals on which yis positive or negative. on which y is decreasing.intervals y concave up or down.points of inflections

I bet you mean
y = 5/(x3) ????
if so then
approches zero at  infinity and + infinity
undefined at x = 3
negative between x = oo and x = 3
positive between x = 3 and x = +oo
decreasing for all x except exactly as x = 3
In other words goes down from 0 to oo as x goes from oo to 3
then goes down from +oo to 0 as x goes from 3 to +oo