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Question
Simplify using following identity : `( a +- b )(a^2 +- ab + b^2) = a^3 +- b^3`
`(a/3 - 3b)(a^2/9 + ab + 9b^2)`
Solution
`(a/3 - 3b)(a^2/9 + ab + 9b^2)`
= `(a/3 - 3b)[(a/3)^2 + (a/3)(3b) + (3b)^2]`
= `(a/3)^3 - (3b)^3`
= `a^3/27 - 27b^3`
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