Question 193956
these  are  conjugates,  use  distribution  techniques  to  resolve,  in  fact  use  FOIL  here,
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(p-sqrt(n) )  *  (p+sqrt(n) )
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p^2  +p sqrt(n)  - p sqrt(n) - sqrt(n) sqrt(n),,,,,,,,,,,note  +psqrtn -psqrtn =0,  typical  of  conjugates
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p^2  - sqrt (n)^2,,,,,,note  sqrtn^2=n
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p^2 -n
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check
let  n=4, p=3,,,,use  calculator  on  original  and  answer,  both  gave (5),,,ok