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Find the least positive value of x such that

89 ≡ (x + 3) (mod 4)

is a multiple of

User Mithir
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1 Answer

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Answer: To find the least positive value of x that satisfies the given congruence, we can use the trial and error method or algebraic manipulation.

Using the trial and error method, we can start by plugging in values of x and checking if the congruence is satisfied.

For x = 1, (x + 3) = 4, so 89 ≡ 0 (mod 4), which is not a multiple of 3.

For x = 2, (x + 3) = 5, so 89 ≡ 1 (mod 4), which is not a multiple of 3.

For x = 3, (x + 3) = 6, so 89 ≡ 2 (mod 4), which is not a multiple of 3.

For x = 4, (x + 3) = 7, so 89 ≡ 3 (mod 4), which is not a multiple of 3.

For x = 5, (x + 3) = 8, so 89 ≡ 0 (mod 4), which is a multiple of 3.

Therefore, the least positive value of x that satisfies the congruence is x = 5.

Alternatively, we can use algebraic manipulation to solve the congruence. We have:

89 ≡ (x + 3) (mod 4)

=> 89 ≡ x + 3 (mod 4)

=> 86 ≡ x (mod 4) (subtracting 3 from both sides)

Now we need to find the least positive value of x that satisfies this congruence and is a multiple of 3.

The solutions for this congruence are x = 2 (mod 4) and x = 6 (mod 4).

Plugging in x = 2, we get 89 ≡ 5 (mod 4), which is not a multiple of 3.

Plugging in x = 6, we get 89 ≡ 3 (mod 4), which is not a multiple of 3.

Therefore, the least positive value of x that satisfies the congruence and is a multiple of 3 is x = 10 (which is equivalent to x = 2 (mod 4) and x = 6 (mod 4)), but this is not the answer to the original question since x must be positive.

Plugging in x = 14, we get 89 ≡ 1 (mod 4), which is not a multiple of 3.

Plugging in x = 18, we get 89 ≡ 3 (mod 4), which is not a multiple of 3.

Finally, plugging in x = 22, we get 89 ≡ 1 (mod 4), which is not a multiple of 3.

Plugging in x = 26, we get 89 ≡ 3 (mod 4), which is not a multiple of 3.

Since we want x to be positive, we can stop here and conclude that the least positive value of x that satisfies the given congruence is x = 5.

Explanation:

User Griflet
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