In: Advanced Math
Classify each function as injective, surjective, bijective, or none of these.
a) f1 : N --> Q defined by f1 (n) = n/(n+1)
b) f2: Z --> Z defined by f2(n) = n2
c) f3 : N --> N defined by f3(n) = n3
d) f4 : B --> (0, infinity) defined by f4 (C) = the area of C, where B is the set of all circles in the firs quadrant that are simultaneously tangent to both the positive x and y axes.
e) f5: A --> (0, infinity) defined by f5(R) = the area of R, where A is the set of all "not-taller-than-wide" rectangles in the first quadrant with on e angle at the origin (i.e., the one side lying along the positive x-axis and another side lying along the positive y-axis, and the width of any rectangle in A is greater than or equal to its height).