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If x3 + y3 = 243 and x + y = 9, then find the value of xy.1. 92. 183. 274. 36 |
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Answer» Correct Answer - Option 2 : 18 Given: x3 + y3 = 243 x + y = 9 Formula used: (x + y)3 = x3 + y3 + 3xy(x + y) Calculations: x + y = 9 Cubing on both the sides, (x + y)3 = 729 ⇒ x3 + y3 + 3xy(x + y) = 729 ⇒ 243 + 3xy × 9 = 729 ⇒ 27xy = 486 ⇒ xy = 18 ∴ The value of xy is 18 |
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