Question

Answer 1

\(A=1-2+3-4+5-6+7-...-100+101\\ =\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+...+\left(99-100\right)+101\\ =\left(-1\right)+\left(-1\right)+\left(-1\right)+...+\left(-1\right)+101\\ =\left(-1\right)\times50+101\\ =-50+101\\ =51\)

Answer 2

A=1−2+3−4+5−6+7−...−100+101
=(1−2)+(3−4)+(5−6)+...+(99−100)+101
=(−1)+(−1)+(−1)+...+(−1)+101
=(−1)×50+101=−50+101=51