题目

计算或化简： ① ② ③ ④ 答案：解：① −15−(−5)−(+8)+(−34) = −15+5−8−34 =-52 ② −22+(1−15×0.2)÷(−2)3 = −4+(1−15×15)÷(−8) = −4−(1−125)×18 = −4−2425×18 = −4−325 = −4325 ③ 5x2y−4xy2−3x2y+2xy2+1 = (5x2y−3x2y)+(2xy2−4xy2)+1 =2x2y-2xy2+1； ④ −3(m2−2m−1)−(2m2−3m)−3 = −3m2+6m+3−2m2+3m−3 = (−3m2−2m2)+(3m+6m)+(3−3) =-5m2+9m．

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