My main trouble is with two points in this solution. The first is the middle part where [math](\sqrt{x + 15}- \sqrt{x } \times 15 = 15[/math] appears and i don't now how or why. Also i don't know why the +1 in the 15+1 is there in the last part of the solution. All help is greatly appreciated.

My main trouble is with two points in this solution. The first is the middle part where [math](\sqrt{x + 15}- \sqrt{x } \times 15 = 15[/math] appears and i don't now how or why. Also i don't know why the +1 in the 15+1 is there in the last part of the solution. All help is greatly appreciated.

Let:
\(\displaystyle (\sqrt{x+15}) - \sqrt{x})\) = A ................................ and ...............................................................................................(1)

\(\displaystyle (\sqrt{x+15}) + \sqrt{x})\) = B ...........................Then from given problem statement B = 15 ......................(2)

It was shown that (using \(\displaystyle (m + n) * (m - n) =m^2 - n^2\))

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