Chapter 14 - Sequences, Series, and the Binomial Theorem - 14.4 The Binomial Theorem - 14.4 Exercise Set - Page 921: 4

Third

To use Pascal's triangle to expand $(x+y)^2$ we us the third row of coefficients. In the third row, we have the coefficients: $\binom{2}{0}, \binom{2}{1}, \binom{2}{2}$ In the expansion of $(x+y)^2$: $\binom{2}{0}x^2y^0+\binom{2}{1}x^1y^1+\binom{2}{2}x^0y^2$