数优化37一7,87.已知|4+a|+(a-2b)²=0,则a+2b___________8.若三个有理数满足xyz>0,则|x|/x+|y|/y+|z|/z=____________
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![数优化37一7,87.已知|4+a|+(a-2b)²=0,则a+2b___________8.若三个有理数满足xyz>0,则|x|/x+|y|/y+|z|/z=____________](/uploads/image/z/12873100-4-0.jpg?t=%E6%95%B0%E4%BC%98%E5%8C%9637%E4%B8%807%2C87.%E5%B7%B2%E7%9F%A5%7C4%2Ba%7C%2B%28a-2b%29%26sup2%3B%3D0%2C%E5%88%99a%2B2b___________8.%E8%8B%A5%E4%B8%89%E4%B8%AA%E6%9C%89%E7%90%86%E6%95%B0%E6%BB%A1%E8%B6%B3xyz%EF%BC%9E0%2C%E5%88%99%7Cx%7C%2Fx%2B%7Cy%7C%2Fy%2B%7Cz%7C%2Fz%3D____________)
数优化37一7,87.已知|4+a|+(a-2b)²=0,则a+2b___________8.若三个有理数满足xyz>0,则|x|/x+|y|/y+|z|/z=____________
数优化37一7,8
7.已知|4+a|+(a-2b)²=0,则a+2b___________
8.若三个有理数满足xyz>0,则|x|/x+|y|/y+|z|/z=____________
数优化37一7,87.已知|4+a|+(a-2b)²=0,则a+2b___________8.若三个有理数满足xyz>0,则|x|/x+|y|/y+|z|/z=____________
7.|4+a|+(a-2b)²=0
即:|4+a|=0
(a-2b)²=0
4+a=0
a-2b=0
解得:
a=-4
b=-2
则a+2b=-4-4=-8
8.xyz>0
有2种情况:
①三个数都大于0
x>0 y>0 z>0
即|x|=x |y|=y |z|=z
则|x|/x+|y|/y+|z|/z=x/x+y/y+z/z=1+1+1=3
②一个数大于0,令两个数小于0
不妨设:x>0 y