Find the first three terms of the expansion of ${{(1+ax)}^{9}}$ where $a$ is a constant. The coe

Question

Find the first three terms of the expansion of ${{(1+ax)}^{9}}$ where $a$ is a constant. The coefficient of ${{x}^{2}}$ in the expansion of $(2-x){{(1+ax)}^{9}}$ is zero. Find the value of $a$.

Accepted Answer

$1+9ax+36a^2x^2+\cdots$; $a=0$ or $a=\frac18$.

Binomial Theorem - Binomial Expansion for Positive Integer Powers

Binomial Theorem - Binomial Expansion for Positive Integer Powers

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