已知x+y=5 ① y+z=-2 ② z+x=3 ③,求x+y+z的值

问题描述:

已知x+y=5 ① y+z=-2 ② z+x=3 ③,求x+y+z的值

x+y+z
=(x+y+y+z+z+x)÷2
=(5-2+3)÷2
=3

x+y=5 ① y+z=-2 ② z+x=3 ③,
①+ ②+③
2(x+y+z)=6
x+y+z=3

已知x+y=5 ① y+z=-2 ② z+x=3 ③,求x+y+z的值
①+②+③得
2x+2y+2z=6
所以x+y+z=3.