若(5x-7y-31)²+(x+y-5)的绝对值=0,求3x+2y的值.
问题描述:
若(5x-7y-31)²+(x+y-5)的绝对值=0,求3x+2y的值.
答
(5x-7y-31)²+(x+y-5)的绝对值=0
所以5x-7y-31=0(1)
x+y-5=0 (2)
(1)+(2)×7
5x-7y-31+7x+7y-35=0
12x=66
所以x=11/2
y=5-x=-1/2
所以3x+2y
=33/2-1
=31/2