# Answer to Question #1839 in Discrete Mathematics for Gloria Parlatore

Question #1839

Give examples of functions N to N that are:

a) one-to-one but NOT onto

b) onto but NOT one-to-one

c) both

d) neither one-to-one nor onto

a) one-to-one but NOT onto

b) onto but NOT one-to-one

c) both

d) neither one-to-one nor onto

Expert's answer

a) for example, exponenta: e

b) x = b,

c) straight line (y = ax + b, if a<>0)

d) parabola, y= x

^{x};b) x = b,

c) straight line (y = ax + b, if a<>0)

d) parabola, y= x

^{2}; or modulus: y = |x+2|.
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