Q. 113.9( 8 Votes )

If x- y = 7 and xy = 9, find the value fo x2+y2

Answer :

Given that, x – y = 7

Squaring both sides, we get

(x – y)2 = (7)2

x2 + y2 – 2xy = 49

Its given that xy = 9, 

x2 + y2 – 2 (9) = 49

x2 + y2 = 49 + 18

x2 + y2 = 67

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