SOLUTION: If x-y = 7, xy= -8, What is the value of x^2 + 3xy + y^2 ?

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Question 894316: If x-y = 7, xy= -8, What is the value of x^2 + 3xy + y^2 ?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
%28x-y%29%5E2=x%5E2-2xy%2By%5E2
So then,
%28x-y%29%5E2%2B5xy=x%5E2-2xy%2By%5E2%2B5xy
%28x-y%29%5E2%2B5xy=x%5E2%2B3xy%2By%5E2
Substituting,
x%5E2%2B3xy%2By%5E2=7%5E2%2B5%28-8%29
x%5E2%2B3xy%2By%5E2=49-40
x%5E2%2B3xy%2By%5E2=9