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Example 1 (Method 1) Find the square of the following numbers without actual multiplication. (i) 39 We know that 39 = 40 − 1 Now, 392 = (40 − 1)2 = 402 + 12 − 2 × 40 × 1 = 1600 + 1 − 80 = 1601 − 80 = 1521 Example 1 (Method 2) Find the square of the following numbers without actual multiplication. (i) 39 We know that 39 = 30 + 9 Now, 392 = (30 + 9)2 = 302 + 92 + 2 × 30 × 9 = 900 + 81 + 540 = 1521

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.