Question 131

The sum of all the coefficients in the expansion of $$(1 - 2x + 3x^2)^9$$ is

$$(1 - 2x + 3x^2)^9$$

substitute  x=1

$$(1 - 2\times1 + 3\times1^2)^9$$

$$(1 - 2 + 3)^9$$

$$(2)^9$$

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