Question

If a=3+b find value of a^3 -b^3-9ab.
Plz answer detail .

Answer 1

Hey friend!!

Here's ur answer..


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$a = 3 + b \\ \\ {a}^{3} - {b}^{3} - 9ab \\ \\ = (3 + b {)}^{3} - {b}^{3} - 9(3 + b)b \\ = 27 + {b}^{3} + 27b + 9 {b}^{2} - {b}^{3} - 9(3b + {b}^{2} ) \\ = 27 + 27b + 9 {b}^{2} - 27b - 9 {b}^{2} \\ \\ = 27$



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