What is the coefficient of the third term in the binomial expansion of open paren A plus b close paren to the 6th power ?

In the expansion of (A + b)^6, the coefficients come from the binomial coefficients in row 6 of Pascal’s triangle: 1, 6, 15, 20, 15, 6, 1. The third term uses the third coefficient, 15, so the correct choice is 15.

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