Question

y=5/x-3
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

Answer 1

I bet you mean
y = 5/(x-3) ????
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