Question

if and b are two odd positive integers such that a>b, then prove that one of the two numbers (a+b/2) and (a-b/2) is odd the other is even

Answer 1

Given:

If a and b are two odd positive integers such that a > b.

Prove:

That one of the two numbers (a + b)/2 and (a – b)/2 is odd and the other is even.

Proof:

Let a and b be any odd odd positive integer such that a > b

Since any positive integer is of the form q, 2q + 1

Let a = 2q + 1 and b = 2m + 1,

Where, q and m are some whole numbes.

=> a + b/2 = (2q + 1) - (2m + 1) / 2

=> a + b/2 = 2(q + m) + 1 / 2

=> a + b/2 = (q + m + 1) / 2

Which is a positive integer.

Also,

=> a - b/2 = (2q + 1) - (2m + 1) / 2

=> a - b/2 = 2(q - m) / 2

=> a - b/2 = (q - m)

Given a > b

Therefore,

=> 2q + 1 > 2m + 1

=> 2q > 2m

=> q = m

Therefore,

=> a + b / 2 = (q - m) > 0

Thus,

(a + b)/2 is a positive integer.

Now,

Prove that one of the two numbers (a + b)/2 and (a – b)/2 is odd and the other is even.

=> (a + b)/2 - (a – b)/2

=> (a + b) - (a - b) / 2

=> 2b/2

=> b

b is odd positive integer.

Also,

The proof above that (a + b)/2 and (a - b)/2 are positive integers.

Hence, it is proved that if a and b are two odd positive integer such that a > b then one of the two numbers (a + b)/2 and (a - b)/2 is odd and the other is even.

I hope it will help you.

Regards.

Answer 2

Answer:

Let the present age of Aaron be 'x' years.

Let the present age of Ron be 'y' years

Aaron is 5 years younger than Ron

=> x = y + 5 .......(i).

4 years later Aaron will be twice as old as Ron

Aaron's age = (x+ 4) years

Ron's age = (y+4) years

=> (x + 4) = 2(y + 4

Step-by-step explanation: