Q15 of 95 Page 93

If x – y = 7 and xy = 9, find the value of (x2 + y2).

x – y = 7 (given)


By squaring both the sides we get;


= (x – y)2 = (7)2


= x2 + y2 – 2xy = 49


= x2 + y2 = 49 + 2xy


Also given,


xy = 9


= x2 + y2 = 49 + 2(9)


= x2 + y2 = 49 + 18


= x2 + y2 = 67


So, the value of x2 + y2 is 67.






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