计算下列各题(要求写出解题关键步骤): (1)3-2×(-5)2; (2)-22-(-3)3×(-1)4-(-1)5; (3)[(-
(4)
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(1)原式=3-2×25
=3-50
=-47;
(2)原式=-4-(-27)-(-1)
=-4+27+1
=24;
(3)原式=[-
×27 8
×(-2)-9-(-27)]×(-1)16 9
=(12-9+27)×(-1)
=-30;
(4)原式=[-8×(-1)-13÷(-
)]÷{1+[1-9×(-2)}1 4
=(8+52)÷(1+1+18)
=3.