Question

using identity 7.87×7.87-2.13×2.13
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Answer 1

Answer:

7.87×7.87 - 2.13×2.13

= (7.87)² - (2.13)²

= (7.87 + 2.13)(7.87 - 2.13)

{a² - b² = (a+b)(a-b)}

= 10×5.74

= 57.40