Question

For any two numbers a and b. If 3 is the least prime factor of a and 7 is the least prime factor of b. then find the least prime factor of (a+b)?​

Answer 1

Answer:

I don't know answer

I don't know answer

Answer 2

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Since 7+ 3 = 10

• The least prime factor of a+b has to be 2; unless a +b is a prime number greater than 2.

• Suppose a +b is a prime number greater than 2. Then a+b must be an odd number

• one of a or b must be an even number. Suppose then that a is even. Then the least prime factor of a is 2; which is not 3 or 7. So a can not be an even number nor can b be an even number.

• Hence a+b can not be a prime number greater than 2 if the least prime factor of a is 3 and b is 7.

• Thus the answer is 2.