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Question
Write in the expanded form:
(2a - 3b - c)2
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Solution
We have
`(2a - 3b - c)^2 = [(2a) + (-3b) +(-c)]^2`
`= (2a)^2 + (-3b)^2 + (-c)^2 + 2(2a)(-3b) + 2(-3b)(-c) + 2(2a)(-c)`
`[∵ (a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc = 2ca]`
`= 4a^2 + 9b^2 + c^2 - 12ab + 6bc - 4ac`
`∴ (2a - 3b - c)^2 = 4a^2 + 9b^2 + c^2 - 12ab + 6bc - 4ca`
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