If x + y = 7, then what is the value of x3 + y3 + 21xy ?
Answer : Option D
Explanation : x + y = 7 (Given)
∴ (x + y)³ = 7³ = 343
⇒ x³ + y³ + 3xy (x + y) = 343
⇒ x³ + y³ + 21xy = 343
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If x + y = 7, then what is the value of x3 + y3 + 21xy ?
x + y = 7 (Given)
∴ (x + y)³ = 7³ = 343
⇒ x³ + y³ + 3xy (x + y) = 343
⇒ x³ + y³ + 21xy = 343