`a)``|x+3/4|+|y-1|=0`

Ta có:`{(|x+3/4|>=0AAx),(|y-1|>=0AAy):}`

`=>|x+3/4|+|y-1|>=0AAx,y`

Dấu "=" xảy ra `<=>{(x+3/4=0),(y-1=0):}`

`=>{(x=-3/4),(y=1):}`

Vậy `x=-3/4;y=1`

`b)``|x-1/2|+|y-1/3|+|x+y+z|=0`

Ta có:`{(|x-1/2|>=0AAx),(|y-1/3|>=0AAy),(|x+y+z|>=0AAx;y;z):}`

`=>|x-1/2|+|y-1/3|+|x+y+z|>=0AAx,y,z`

Dấu "=" xảy ra `<=>{(x-1/2=0),(y-1/3=0),(x+y+z=0):}`

`=>{(x=1/2),(y=1/3),(z=0-x-y):}`

`=>{(x=1/2),(y=1/3),(z=-5/6):}`

Vậy `x=1/2;y=1/3;z=-5/6`