\(A=100+98+96+...+2-1-3-...-95-97\)
\(A=\left(100+98+96+...+2\right)+\left(-1-3-...-95-97\right)\)
\(A=\sum\limits^{50}_{x=1}\left(x\cdot2\right)+\left(\sum\limits^{-48}_{x=0}\left(x\cdot2-1\right)\right)\)
\(A=2550+\left(-2401\right)\)
\(A=149\)
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