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:
It is an obtuse triangle I think because
3y - 12 = -6
3y = 6 | Add 12 to both sides
y = 2 | Divide by 3 on both sides
Answer: y = 2 (Answer B)
Is that supposed to be x squared, or x times 2 in the beginning of the first one?
Answer:
25
Step-by-step explanation:
15/6.0=2.5
2.5x4=10
2.5x6=15
10+15=25
10 boys and 15 girls
