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Test 7 question 7 of 20, need help?
If x² + y² =1, and the average of x + y =4, what is x – y?
I don't even know where to start with this one , but I need to learn how to solve them so I'm hoping for an explanation.
Thank you
1 Answer
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- ?Lv 68 years agoFavorite Answer
I will start from (x+y)^2 =x^2+y^2+2xy, then we got:
16=1+2xy
2xy=15
Then, we use another equation, like:
(x-y)^2=x^2-2xy+y^2
x-y=sqrt(1-15)
x-y=14i, where i=sqrt(-1)
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