用计算器计算:
(1)(﹣32.5)÷(0.25)﹣(﹣7.8)×3;
(2)(﹣5)2﹣2×(﹣3)2;
(3)[﹣12×5﹣81÷(﹣9)]×(﹣2)4.
解:(1)(﹣32.5)÷(0.25)﹣(﹣7.8)×3
=﹣130+23.4
=﹣106.6;
(2)(﹣5)2﹣2×(﹣3)2
=25﹣18
=7;
(3)﹣12×5﹣81÷(﹣9)×(﹣2)4
=(﹣60+9)×16
=﹣816.
如图所示的电路中,电源电压不变,开关闭合后,若滑动变阻器的滑片P向右端移动,则 ( )
School students _____ smoke because it is bad for their health and it is against the law.
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①生态平衡稳定性强 ②生态系统组成单一 ③生态系统结构复杂
④生态平衡稳定性差 ⑤动植物种类繁多 ⑥生态系统结构简单.