Question

Number of integers ab such that ab-ba is a prime

Answer 1

Step-by-step explanation:

b=ab+ba

We can say, ab = ba ( e.g its one and the same thing whether we say 2*3 or 3*2)

So, a+b=ab+ab

a+b=2ab….. (1)

Okay, now lets come to equation, 2a+2b

which is equal to 2(a+b) …….(2)

(taking 2 common)

Now, inserting the value of a+b from (1) in (2)

2(2ab)=4ab

Hence, 2a+2b=4ab

Hope it helps !!