若Y1=-X+3,Y2=3X-4 ,试确定当X取何值时:(1)Y1小于Y2 (2)Y1等于Y2 (3)Y1大于Y2

问题描述:

若Y1=-X+3,Y2=3X-4 ,试确定当X取何值时:(1)Y1小于Y2 (2)Y1等于Y2 (3)Y1大于Y2

(1)Y1即-X+3化简:-4X得X> 7/4
(2) Y1=Y2
即-X+3=3X-4
化简:-4X=-7
得X= 7/4
(3) Y1>Y2
即-X+3>3X-4
化简:-4X>-7
得X

(1)
-x+34+3
4x>7
x>7/4
当x>7/4 Y1小于Y2
(2)
-x+33x-4
x