Answer:

Step-by-step explanation:

Given:

a+2b+3c=0,a+2b=−3c

Let us raise the power to three on both sides, we get

(a+2b)^3

=(−3c)^3

a^3+(2b)^3+3(a)(2b)(a+2b)=−27c^3

a^3+8b^3+6ab(−3c)=−27c^3

a^3+8b^3−18abc=−27c^3

a^3+8b^3+27c^3=18abc

Hence proved.

Step-by-step explanation:

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