Because 2ab/(a=b)=2 1

2ab=2 1a+2 1b

2 1a+2 1b-2ab=0

When a=b, a 2+b 2-2ab = 0.

So a=b=27.

The second way should be the same as above.

But why is the second number "Love you all your life"?

supplement

Get a > 0 and b > 0 from the question. 2ab/(a+b) = 212ab = 21(a+b), then (a+b) 2-(a 2+b 2) = 21(a+b) (a+b 2 a+b > 10.5 < a < 2 1， 10.5 < b < 2 1。 I don't know if it's right.