যদি (a - b) = 3 এবং ab = 70 হয় তবে (a3 - b3) এর মানটি নির্ণয় করুন।

  1. 657
  2. 783
  3. 840
  4. 580

Answer (Detailed Solution Below)

Option 1 : 657
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প্রদত্ত :

(a - b) = 3 এবং ab = 70

সূত্র:

a3 – b3 = (a – b)3 + 3ab(a – b)

গণনা:

a3 – b3 = (a – b)3 + 3ab(a – b)

⇒ a3 – b3 = 33 + 3 × 70 × 3

⇒ a3 – b3 = 27 + 630

∴ a3 – b3 = 657

সংক্ষিপ্ত কৌশল

a = 10 এবং b = 7 [যেহেতু (a – b) = 10 – 7 = 3 এবং ab = 10 × 7 = 70] নিলে

∴ a3 – b3 = 103 – 73 = 1000 – 343 = 657

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