|x|=7,|y|=12,且|x+y|=—(x+y),求x+y的值
问题描述:
|x|=7,|y|=12,且|x+y|=—(x+y),求x+y的值
答
|x|=7,|y|=12,且|x+y|=—(x+y)≥0
即
x+y≤0
所以
-
x=7,y=-12
x+y=7-12=-5
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x=-7,y=-12
x+y=-7-12=-19