设<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/a95fd14e150c4fafad4663c2178326e8.plain?x-oss-process=image/sharpen,200"/> 为负向,<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/5e9a0929f5d849e0bb513c98d78bc3e1.plain?x-oss-process=image/sharpen,200"/> 正向,则<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/6f13a1859d6647a391b6a5f2d9a2d3e2.plain?x-oss-process=image/sharpen,200"/> ( )