In each part sets A and B and a function from A to B are giv

In each part, sets A and B and a function from A to B are given. Determine whether the function is one to one or onto (or both or neither).
A=|R, B= {x | x is real and x > 0}; f(a)= |a|

Solution

Given function is not one one because for positive values of a and negative values of a f(a) is positive

Which tells us that two elements of A has one image in B.

Hence not one one

Given f(a) is onto because all elements of B has a image in A