若根号x+y-1+(y+3)²=0,求(5x-y)·(2x+3y)的值.
问题描述：
若根号x+y-1+(y+3)²=0,求(5x-y)·(2x+3y)的值.
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答
根号x+y-1+(y+3)²=0
则 x+y-1=0,x+y=1
y+3=0,y=-3,x=4
(5x-y)·(2x+3y)
=(20+3)(8-9)
=-23