Find an expression for ∫1n(−1)⌊x⌋⌊x⌋−1 dx\displaystyle\int_1^n(-1)^{\lfloor x\rfloor}\lfloor x\rfloor^{-1}\,dx∫1n(−1)⌊x⌋⌊x⌋−1dx where n∈Nn\in\mathbb{N}n∈N. A∑k=1n(−1)k1k\displaystyle\sum_{k=1}^n(-1)^k\frac1kk=1∑n(−1)kk1B∑k=1n−1(−1)k1k\displaystyle\sum_{k=1}^{n-1}(-1)^k\frac1kk=1∑n−1(−1)kk1C∑k=1n−1(−1)k1k2\displaystyle\sum_{k=1}^{n-1}(-1)^k\frac1{k^2}k=1∑n−1(−1)kk21D∑k=1n(−1)k1k2\displaystyle\sum_{k=1}^n(-1)^k\frac1{k^2}k=1∑n(−1)kk21