Question

Question 21 please help urgent

Answer 1

3x-y=8

(3x-y)^3=8^3

27x^3-y^3-9xy(3x-y)=512

27x^3-y^3-27(8)=512

27x^3-y^3-216=512

27x^3-y^3=512+216=728

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