Giải bài tập 2 trang 37 Chuyên đề toán 10 cánh diều

Bài tập 2. Tính

a) $S= C_{2022}^{0}9^{2022}+C_{2022}^{1}9^{2021}+...+C_{2022}^{k}9^{2022-k}+...+C_{2022}^{2021}9+C_{2022}^{2022}$

b) $T=C_{2022}^{0}4^{2022}-C_{2022}^{1}4^{2021}\times 3+...-C_{2022}^{2021}4\times 3^{2021}+C_{2022}^{2022}3^{2022}$


a) $S= C_{2022}^{0}9^{2022}+C_{2022}^{1}9^{2021}+...+C_{2022}^{k}9^{2022-k}+...+C_{2022}^{2021}9+C_{2022}^{2022}$

$=C_{2022}^{0}9^{2022}+C_{2022}^{1}9^{2021}\times 1+...+C_{2022}^{k}9^{2022-k}\times 1^{k}+...+C_{2022}^{2021}9\times 1^{2021}+C_{2022}^{2022}\times 1^{2022}$

$=(9+1)^{2020}=10^{2022}$

b) $T=C_{2022}^{0}4^{2022}-C_{2022}^{1}4^{2021}\times 3+...-C_{2022}^{2021}4\times 3^{2021}+C_{2022}^{2022}3^{2022}$

 $=C_{2022}^{0}4^{2022}+C_{2022}^{1}4^{2021}\times (-3)^{1}+...-C_{2022}^{2021}4\times (-3)^{2021}+C_{2022}^{2022}(-3)^{2022}$

$=[4+(-3)]^{2022}=1^{2022}=1$


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