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Q: If a³ + b³ = 217 and a + b = 7, then the value of ab is: यदि a³ + b³ = 217 और a + b = 7 है, तो ab का मान ज्ञात करें।
  • A. –1
  • B. 7
  • C. 6
  • D. –6
Correct Answer: Option C - ∵ (a+b)³ = a³ + b³ + 3ab(a+b) (7)³ = 217 + 3ab × 7 343 – 217 = 21ab 126 = 21ab ab = 6
C. ∵ (a+b)³ = a³ + b³ + 3ab(a+b) (7)³ = 217 + 3ab × 7 343 – 217 = 21ab 126 = 21ab ab = 6

Explanations:

∵ (a+b)³ = a³ + b³ + 3ab(a+b) (7)³ = 217 + 3ab × 7 343 – 217 = 21ab 126 = 21ab ab = 6