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:For this item, we let x and y be the number of bushels of apple that will be used to produce apple cider and apple juice, respectively. The situation above is best represented by the following equations,
x + y = 18
20x + 15y = 330
The values of x and y from the equations above are 12 and 6, respectively. Therefore, 12 bushels will be used to make apple cider and 6 bushels will be used to make apple juice.
Step-by-step explanation:
The equation of the circle would be
(
x
−
(
−
4
)
)
2
+
(
y
−
7
)
2
=
6
2
or
(
x
+
4
)
2
+
(
y
−
7
)
2
=
36
