Q. 113.9( 8 Votes )

# If x- y = 7 and xy = 9, find the value fo x^{2}+y^{2}

Answer :

Given that, x – y = 7

Squaring both sides, we get

(x – y)^{2} = (7)^{2}

x^{2} + y^{2} – 2xy = 49

Its given that xy = 9,

x^{2} + y^{2} – 2 (9) = 49

x^{2} + y^{2} = 49 + 18

x^{2} + y^{2} = 67

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If x- y = 7 and xy = 9, find the value fo x^{2}+y^{2}