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:
0.8 lbs
Step-by-step explanation:
Ounces are typically used to measure liquid, so I would discourage choosing the top two. And, hopefully you know by now that an orange does not weigh 8 pounds.
Answer:
Step-by-step explanation:
You have to set each runner's plan equal to each other because they are equal in the end. You start with 7 miles for Angelo and 4 miles for Marc.
x is a variable that is multiplied by the number of weeks it takes for both runners' distances to be equal. So multiply x by the miles increased every week.
Marc = Angelo
2x + 4 = x + 7
x = 3
In 3 weeks each runner will run 10 miles for the week.
Answer:
its b
Step-by-step explanation:
Answer:
1 3/8
Step-by-step explanation:
First, change the mixed fraction to improper fraction.
2 3/4 = 8/4 + 3/4 = 11/4
1/2 of 11/4 = (11/4)(1/2) = 11/8
11/4 - 11/8 = 22/8 - 11/8 = 11/8
11/8, or 1 3/8 is your answer.
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