(1)当X为何值时,M1与M2互为相反数?
2x-1+-x+3=0
=>
x=-2/3
(2)当X为何值时,M1是M2的2倍?
2x-1=2*(-x+3)
=>
x=7/4
(3)当X为何值时,M1比M2小1?
2x-1=-x+3-1
=>
x=1