The function y=1-1/x is often used to show how the repeating decimal 0.9999... is equal to 1. When x=1, y=1; x=10, y=0.9; x=10000, y=.9999, and so on. The limit of 1-1/x as x approaches infinity equals 1. An assumption is often made, however, that if the limit of an expression as x approaches infinity is 1, then that expression must equal 1 when x equals infinity. Assumption: 1-1/x = 1 when x = infinity Subtraction: -1/x = 0 Multiplication: -1 = 0x Zero Property: -1 = 0 -1 does not equal 0, therefore 1-1/x does not equal 1 when x = infinity. You cannot treat "infinity" like a normal number, you can only think of it in terms of limits.