Why is .9 repeating NOT equal to one. 1/3=.333333333333... 1/33=.3333333333333...3 1=.999999999999999999... my math teacher says this is incorrect why is this? pls help.

Because infedecimals. Basically 1 -.99999.... Is a number so close to zero it is impossible to define. If this were infanct the case however and a number existed that was not 0 and not 0 it would wreck mathematics so infedecimals exist only theoretically. So .999... Is equal to 1 practically but not theoretically.