Question

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${\left(1+\frac{2}{3}a\right)}^3$

Answer 1

${(1+\frac{2}{3}a)}^3=1+{\left(\frac{2}{3}a\right)}^3+3\left(\frac{2}{3}a\right)\left(1\right)(\frac{2}{3}a+1)$

$=1+\frac{8}{27}{a}^3+2a(\frac{2}{3}a+1)$

$=1+\frac{8}{27}{a}^3+\frac{4}{3}{a}^2+2a.$

Hence, the answer is $1+\frac{8}{27}{a}^3+\frac{4}{3}{a}^2+2a.$