Thursday, July 4, 2013

if x+y=7*2 and xy =5*2 find x-y

%0D%0A%28x-y%29%5E2+=+x%5E2+-+2+xy+%2B+y%5E2%0D%0A 

%0D%0A%28x%2By%29%5E2+=+x%5E2+%2B+2+xy+%2B+y%5E2%0D%0A 


subtracting...
%0D%0A%28x-y%29%5E2-%28x%2By%29%5E2+=+-4xy+%0D%0A 


and so... 

%0D%0A%28x-y%29%5E2+=%28x%2By%29%5E2+-4xy+=+%2814%2B10%29%5E2-4%2814%29%2810%29=16%0D%0A 


So x-y=4 


:) 

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