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प्रश्न
If x + y = 9, xy = 20
find: x2 - y2.
योग
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उत्तर
x + y = 9, xy = 20
We know (x - y) (x + y)
= x2 - y2
⇒ x2 - y2
= (±1) (9)
= ±9.
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