If a prime number on division by 4 gives a remainder of 1, then that n...
Explanation:
To prove that a prime number, when divided by 4, gives a remainder of 1, can be expressed as the sum of squares of two natural numbers, we need to follow the given steps.
Step 1: Prime Number
Let's consider a prime number, p, which when divided by 4 gives a remainder of 1. So, we can write it as p = 4k + 1, where k is an integer.
Step 2: Expressing p as the Sum of Squares
Our goal is to express p as the sum of squares of two natural numbers. Let's assume that p can be expressed as the sum of squares of two natural numbers, a^2 and b^2, where a and b are natural numbers.
We can write the equation as p = a^2 + b^2.
Step 3: Rearranging the Equation
Rearranging the above equation, we get p - a^2 = b^2.
Step 4: Considering Modulo 4
Now, let's consider the modulo 4 for both sides of the equation.
p - a^2 ≡ b^2 (mod 4)
Since p ≡ 1 (mod 4), we can substitute the value of p in the equation.
1 - a^2 ≡ b^2 (mod 4)
Step 5: Squares Modulo 4
Next, we need to consider the possible values of squares modulo 4.
Any perfect square can only be congruent to 0 or 1 modulo 4. This means that a^2 ≡ 0 or 1 (mod 4), and b^2 ≡ 0 or 1 (mod 4).
Step 6: Substituting Values
Substituting the possible values of a^2 and b^2 in the equation, we get the following possibilities:
1 - 0 ≡ 0 (mod 4) - This is not possible as it contradicts our assumption that p is a prime number.
1 - 0 ≡ 1 (mod 4) - This is not possible as it contradicts our assumption that p is a prime number.
1 - 1 ≡ 0 (mod 4) - This is not possible as it contradicts our assumption that p is a prime number.
1 - 1 ≡ 1 (mod 4) - This satisfies our assumption that p is a prime number.
Conclusion:
From the above analysis, we can conclude that a prime number, when divided by 4 and gives a remainder of 1, can be expressed as the sum of squares of two natural numbers.
Therefore, the correct answer is option 'A' - sum of squares of two natural numbers.