Evaluate, Using (A + B)(A - B)= A2 - B2. 399 X 401 - Mathematics

Evaluate, using (a + b)(a - b)= a² - b².
399 x 401

Sum

399 x 401
= (400 - 1) x (400 + 1)
= (400)² - (1)²
= 160000 - 1
= 159999.

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Chapter 4: Expansions - Exercise 4.1

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