2/(√19+√17) = 2/(√19+√17) * (√19-√17)/(√19-√17) = 2(√19-√17)/(19-17) = √19-√17
2/(√17+√15) = 2/(√17+√15) * (√17-√15)/(√17-√15) = 2(√17-√15)/(17-15) = √17-√15
So we have:
(√19-√17) + (√17-√15) + √15 = √19 - √15
Finally, (√19 - √15) * √19 = 19√19 - 15√19 = 4√19, which is the final result.
2/(√19+√17) = 2/(√19+√17) * (√19-√17)/(√19-√17) = 2(√19-√17)/(19-17) = √19-√17
2/(√17+√15) = 2/(√17+√15) * (√17-√15)/(√17-√15) = 2(√17-√15)/(17-15) = √17-√15
So we have:
(√19-√17) + (√17-√15) + √15 = √19 - √15
Finally, (√19 - √15) * √19 = 19√19 - 15√19 = 4√19, which is the final result.