|x+2y|+√3x-7 + (5y+z)^2=0
上式中为三个非负数之和,其和为0,则这三个非负数必等于0,
即有 x+2y=0 ,3x-7=0,5y+z=0,
解得 x=7/3 y=-7/6 z=35/6
则 x-3y+4z=7/3 - (-7/6)X3+35/6 X 4=
=7/3 + 7/2 +70/3
=77/3 +7/2
=175/6终于懂了，辛苦了！