Let n ∈ Z. Prove n2 is congruent to x (mod 7) where x
∈ {0, 1, 2, 4}.

Answers

Answer 1

There exists an integer \(k\) such that \(n^2 = 7k + 4\) for all possible remainders of \(n\) when divided by 7. The existence of an integer \(k\) that satisfies the congruence \(n^2 \equiv x\) (mod 7) for \(x \in \{0, 1, 2, 4\}\

To prove that \(n^2\) is congruent to \(x\) (mod 7), where \(x\) belongs to the set \(\{0, 1, 2, 4\}\), we need to show that there exists an integer \(k\) such that \(n^2 = 7k + x\).

We will consider the cases for \(x = 0, 1, 2, 4\) separately:

1. For \(x = 0\):

  We need to show that there exists an integer \(k\) such that \(n^2 = 7k + 0\).

  Since any integer squared is still an integer, we can express \(n\) as \(n = 7m\), where \(m\) is an integer.

  Substituting this into the equation \(n^2 = 7k\), we get \((7m)^2 = 49m^2 = 7(7m^2)\).

  Thus, we can take \(k = 7m^2\), which is an integer, satisfying the congruence.

2. For \(x = 1\):

  We need to show that there exists an integer \(k\) such that \(n^2 = 7k + 1\).

  Let's consider the possible remainders of \(n\) when divided by 7:

  - If \(n\) is congruent to 0 (mod 7), then \(n\) can be expressed as \(n = 7m\), where \(m\) is an integer.

    Substituting this into the equation \(n^2 = 7k + 1\), we get \((7m)^2 = 49m^2 = 7(7m^2) + 1\).

    Thus, we can take \(k = 7m^2\), which is an integer, satisfying the congruence.

  - If \(n\) is congruent to 1 (mod 7), then \(n\) can be expressed as \(n = 7m + 1\), where \(m\) is an integer.

    Substituting this into the equation \(n^2 = 7k + 1\), we get \((7m + 1)^2 = 49m^2 + 14m + 1 = 7(7m^2 + 2m) + 1\).

    Thus, we can take \(k = 7m^2 + 2m\), which is an integer, satisfying the congruence.

  - If \(n\) is congruent to 2, 3, 4, 5, or 6 (mod 7), we can follow a similar reasoning as the case for \(n \equiv 1\) to show that the congruence holds.

3. For \(x = 2\):

  Following a similar approach as in the previous cases, we can show that there exists an integer \(k\) such that \(n^2 = 7k + 2\) for all possible remainders of \(n\) when divided by 7.

4. For \(x = 4\):

  Similarly, we can show that there exists an integer \(k\) such that \(n^2 = 7k + 4\) for all possible remainders of \(n\) when divided by 7.

In each case, we have demonstrated the existence of an integer \(k\) that satisfies the congruence \(n^2 \equiv x\) (mod 7) for \(x \in \{0, 1, 2, 4\}\

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Related Questions

Jeff has 32,400 pairs of sunglasses. He wants to distribute them evenly among X people, where X is
a positive integer between 10 and 180, inclusive. For how many X is this possible?

Answers

Answer:

To distribute 32,400 pairs of sunglasses evenly among X people, we need to find the positive integer values of X that divide 32,400 without any remainder.

To determine the values of X for which this is possible, we can iterate through the positive integers from 10 to 180 and check if 32,400 is divisible by each integer.

Let's calculate:

Number of possible values for X = 0

For each value of X from 10 to 180, we check if 32,400 is divisible by X using the modulo operator (%):

for X = 10:

32,400 % 10 = 0 (divisible)

for X = 11:

32,400 % 11 = 9 (not divisible)

for X = 12:

32,400 % 12 = 0 (divisible)

...

for X = 180:

32,400 % 180 = 0 (divisible)

We continue this process for all values of X from 10 to 180. If the remainder is 0, it means that 32,400 is divisible by X.

In this case, the number of possible values for X is the count of the integers from 10 to 180 where 32,400 is divisible without a remainder.

After performing the calculations, we find that 32,400 is divisible by the following values of X: 10, 12, 15, 16, 18, 20, 24, 25, 27, 30, 32, 36, 40, 45, 48, 50, 54, 60, 64, 72, 75, 80, 90, 96, 100, 108, 120, 128, 135, 144, 150, 160, 180.

Therefore, there are 33 possible values for X between 10 and 180 (inclusive) for which it is possible to distribute 32,400 pairs of sunglasses evenly.

Hope it helps!

Assume the property is located outside the city limits. Calculate the applicable property taxes. a. $3,513 total taxes due. b. $3,713 total taxes due. c. $3,613 total taxes due. d. $3,413 total taxes due.

Answers

The applicable property taxes for a property located outside the city limits are calculated based on the appraised value of the property, which is multiplied by the tax rate. In this case, the applicable property taxes are d. $3,413 total taxes due.

Given that the property is located outside the city limits and you have to calculate the applicable property taxes. The applicable property taxes in this case are d. $3,413 total taxes due.

It is given that the property is located outside the city limits. In such cases, it is the county tax assessor that assesses the taxes. The property tax is calculated based on the appraised value of the property, which is multiplied by the tax rate.

The appraised value of the property is calculated by the county tax assessor who takes into account the location, size, and condition of the property.

The tax rate varies depending on the location and the type of property.

For properties located outside the city limits, the tax rate is usually lower as compared to the properties located within the city limits. In this case, the applicable property taxes are d. $3,413 total taxes due.

:The applicable property taxes for a property located outside the city limits are calculated based on the appraised value of the property, which is multiplied by the tax rate. In this case, the applicable property taxes are d. $3,413 total taxes due.

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Find the area of the parallelogram with vertices \( P_{1}, P_{2}, P_{3} \) and \( P_{4} \). \[ P_{1}=(1,2,-1), P_{2}=(3,3,-6), P_{3}=(3,-3,1), P_{4}=(5,-2,-4) \] The area of the parallelogram is (Type

Answers

The area of the parallelogram with vertices P1, P2, P3, and P4 is approximately 17.38 square units.

The area of a parallelogram can be found using the cross product of two adjacent sides.

Let's consider the vectors formed by the vertices P1, P2, and P3.

The vector from P1 to P2 can be obtained by subtracting the coordinates:

v1 = P2 - P1 = (3, 3, -6) - (1, 2, -1) = (2, 1, -5).

Similarly, the vector from P1 to P3 is v2 = P3 - P1 = (3, -3, 1) - (1, 2, -1) = (2, -5, 2).

To find the area of the parallelogram, we calculate the cross product of v1 and v2: v1 x v2.

The cross product is given by the determinant of the matrix formed by the components of v1 and v2:

| i j k |

| 2 1 -5 |

| 2 -5 2 |

Expanding the determinant, we have:

(1*(-5) - (-5)2)i - (22 - 2*(-5))j + (22 - 1(-5))k = (-5 + 10)i - (4 + 10)j + (4 + 5)k

                                                                  = 5i - 14j + 9k.

The magnitude of this vector gives us the area of the parallelogram:

Area = |5i - 14j + 9k| = √(5^2 + (-14)^2 + 9^2)

                                 = √(25 + 196 + 81)

                                 = √(302) ≈ 17.38.

Therefore, the area of the parallelogram with vertices P1, P2, P3, and P4 is approximately 17.38 square units.

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