Binomial plzzzzz?

Hint: (1-2x+x²)ⁿ = ((x-1)²)ⁿ = (x-1)²ⁿ
Look at Pascal's triangle. The only entries equal to 66 are in the expansion of (a+b)¹², so n = 6
:::::
x² is the 11th term in the expansion of (x-1)¹², so x³ is the 10th term in the expansion.
coefficient of x³ = 12!/(9!3!) = 10·11·12/(2·3) = 220

6 and -220

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