Jawabanmu

2014-03-24T20:55:24+07:00
Xy= a 
 \frac{1}{x} + \frac{1}{y} = b
 \frac{y}{xy} +  \frac{x}{xy} = b
 \frac{x+y}{xy} = b
x+y = bxy = ab


x² + y² = (x+y)² - 2xy
           = (ab)² - 2a
           = a²b² - 2a
           = a(ab²-2)