Answer:
Consider f: N → N defined by f(0)=0 and f(n)=n-1 for all n>0.
Step-by-step explanation:
First we will prove that f is surjective. Let y∈N be any natural number. Define x as the number x=y+1. Then x∈N, and f(x)=x-1=(y+1)-1=y. We conclude that f is surjective.
However, f is not injective. Take x1=0 and x2=1. Then x1≠x2 but f(x1)=0 and f(x2)=x2-1=1-1=0. We have shown that there are two natural numbers x1,x2 such that x1≠x2 but f(x1)=f(x2), that is, f is not injective.
Note:
If 0∉N in your definition of natural numbers, the same reasoning works with the function f: N → N defined by f(1)=1 and f(n)=n-1 for all n>1. The only difference is that you consider x1=1, x2=2 for the injectivity.
Answer:
136
Step-by-step explanation
multiply 4 by 31 and add 20
Answer:
True
Step-by-step explanation:
The year is typically divided into equal different lengths of time. There are, for example, quarters, which divide the year by 4, i. e., in 4 periods of 3 months each. Other example are semesters, in this case, the year is divided into 2 periods of 6 months each. Taking this into account, an interest calculated on a balance every three months is compounded quarterly.
You add the legnths of the sides together exg
if you have rectangle with width=2 legnth=3
permiter=w+w+l+l=2+2+3+3=10
