"∵x的倒数和绝对值都是它本身,y、z是有理数,并且|y+3|+（2x+3z）^2=0∴x=1 y+3=0 2x+3z=0 x=1 y=-3 x=-2/3∴(5x-2xz)/(-x^3＋y^2-5)=(5+4/3)/(-1+9-5)=(19/3)/3=19/9