Find all positive integers n such that n^4- 1 is divisible by 5.

All positive integers except multiple of 5.

Step-by-step explanation:

From the rule of divisibility, a number's last digit should be either 0 or 5 for it to be divisible by 5.

For to be a multiple of 5, the last digit of should be 0 or 5. In other words, the last digit of should be 1 or 6.

The last digit of is 1 if is an odd number except those that are multiples of 5.

The last digit of is 6 if is an even number except those that are multiples of 5.

Therefore, the possible values of are all positive integers except those that are multiples of 5.

it costs $20 to interview each person for a survey. find the cost to obtain a +- 3% margin of error.

step-by-step explanation:

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i cant see the graph

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