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If (x + y)^2 = 78$ and $xy = 13$, what is $(x - y)^2

 May 14, 2019

Best Answer 

 #1
avatar+4586 
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(x+y)^2=x^2+y^2+2xy.

 

x^2+y^2+2(13)=78, x^2+y^2=52.

 

(x-y)^2=x^2+y^2-2ab, so 52-2(13)=52-26=26-answer.

 May 14, 2019
 #1
avatar+4586 
+1
Best Answer

(x+y)^2=x^2+y^2+2xy.

 

x^2+y^2+2(13)=78, x^2+y^2=52.

 

(x-y)^2=x^2+y^2-2ab, so 52-2(13)=52-26=26-answer.

tertre May 14, 2019

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