Answer:
X = {0, 1, 2, 3, 4}
Step-by-step explanation:
If X is the number of nonzero digits in a 4-digit PIN with no restriction on the digits, the pin can have up to 4 nonzero digits.
Let's see some examples:
If the PIN is 0000 then X = 4
If the PIN is 2045 then X = 3
If the PIN is 7546 then X = 0
From the previous examples, we can see that the possible values for X are 0, 1, 2, 3, 4.
Thus X = {0, 1, 2, 3, 4}
No.
Any number you can write completely is a rational number.
Any number with a repeating decimal fraction is also a rational number.
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Any number that goes on forever without repeating is an irrational number. These are usually represented symbolically (because they cannot be written "exactly" any other way). These include such numbers as √2, π, e, ∛(-4), and an infinite number of others.
There are two methods I know. hope it'd help :)