Answer:
a. closed under addition and multiplication
b. not closed under addition but closed under multiplication.
c. not closed under addition and multiplication
d. closed under addition and multiplication
e. not closed under addition but closed under multiplication
Step-by-step explanation:
a.
Let A be a set of all integers divisible by 5.
Let
∈A such that 
Find 

So,
is divisible by 5.

So,
is divisible by 5.
Therefore, A is closed under addition and multiplication.
b.
Let A = { 2n +1 | n ∈ Z}
Let
∈A such that
where m, n ∈ Z.
Find 

So,
∉ A

So,
∈ A
Therefore, A is not closed under addition but A is closed under multiplication.
c.

Let
but
∉A
Also,
∉A
Therefore, A is not closed under addition and multiplication.
d.
Let A = { 17n: n∈Z}
Let
∈ A such that 
Find x + y and xy


So,
∈ A
Therefore, A is closed under addition and multiplication.
e.
Let A be the set of nonzero real numbers.
Let
∈ A such that 
Find x + y

So,
∈ A
Also, if x and y are two nonzero real numbers then xy is also a non-zero real number.
Therefore, A is not closed under addition but A is closed under multiplication.
Answer:
Step-by-step explanation:
so they used a total of 560 units
we are next told that if the units of usage are 360 or less use the 1st formula, but there is morn than 360 units in the given amount so use the 2nd formula
0.1(x-360+54)
0.1(560-360) + 54 = monthly bill
20+54 = monthly bill
74 = monthly bill
answer D looks good
Happy New Years to you as well! Stay safe
Answer:
1130.97
Step-by-step explanation:
It was easy!
Answer:
Step-by-step explanation:
-49 because 7 multiplied by its self is 49 and since the exponent is negative its -49.I THINKKKKK DON'T KILL ME IF YOU GET IT WRONG.