tatane90 wrote:

if xy != 0, is (1/x + 1/y) = 2 ?

1) x=y

2) x+y = 2xy

Any idea ?

Thanks

1. say x=y=2 xy=4 1/2+1/2 != 2

BUT x=y=1 xy=1 1/1 +1/1 = 2! so INSUFF

2.

you could see it another way - if x and y are the same then their sum equals to 2x or 2y and that cant be 2xy. the only way to be 2xy is if one of them is 1. so..

1 +y = 2(1)y = 1+y =2y. so y has to be 1 to satisfy 2y there fore 1/1 +1/1 =2 so SUFF

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