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प्रश्न
If x – y = 13 and xy = 28, then find x2 + y2.
उत्तर
Given, x – y = 13 and xy = 28
Since, (x – y)2 = x2 + y2 – 2xy ...[Using the identity, (a – b)2 = a2 + b2 – 2ab]
∴ (13)2 = x2 + y2 – 2 × 28
⇒ x2 + y2 = (13)2 + 56
⇒ x2 + y2 = 169 + 56
⇒ x2 + y2 = 225
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