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Question
Using identity, find the value of (1.9) × (2.1)
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Solution
(1.9) × (2.1) = (2 – 0.1) × (2 + 0.1)
Substituting a = 2 and b = 0.1 in
(a – b)(a + b) = a2 – b2 we have
(2 – 0.1)(2 + 0.1) = 22 – (0.1)2
(1.9) × (2.1) = 4 – 0.01
(9.9)(2.1) = 3.99
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