第47页

信息发布者:
D
17
解:原式​$=−1−\frac 32×\frac 13 ×(−\frac 14)$​
​$=−1+\frac 18= −\frac 78$​
解:原式​$=(−4)×(−\frac 57)×(−\frac 74)−\frac 14$​
​$=−5−\frac 14 =-5\frac 14.$​
解:原式​$=−1−[−27−(3−1)÷(−2)]=−1−(−27+ 1)=−1−(−26)=25.$​
解:原式​$=\frac 92 ×[−9×\frac 19−\frac 45]−2\frac 14$​
​$=\frac 92 × (−1−\frac 45)−2\frac 14$​
​$=\frac 92×(−\frac 95)−2\frac 14$​
​$=−8.1−2.25$​
​$=−10.35.$​
解: (1) $2※4 = 2×4 + 1 = 9;$
(2) $1※4 = 1×4 + 1 = 5,$$5※(-2) = 5×(-2) + 1 = -9;$
(3) 选择$-1$和$2,$$-1※2 = (-1)×2 + 1 = -1,$$2※(-1) = 2×(-1) + 1 = -1,$则$-1※2 = 2※(-1)$(答案不唯一)
0
1
2
解: (1) 0,1,2;
(2) 第$n$个等式为$2^n - 2^{n-1} = 2^{n-1},$验证:左边$= 2^{n-1}(2 - 1) = 2^{n-1},$右边$= 2^{n-1},$左边=右边,等式成立;
(3) 设$S = 2^1 + 2^2 + 2^3 + \cdots + 2^{2024},$由
(2)知$2^k = 2^k - 2^{k-1} + 2^{k-1},$则$S = (2^2 - 2^1) + (2^3 - 2^2) + \cdots + (2^{2025} - 2^{2024}) = 2^{2025} - 2^1 = 2^{2025} - 2$