(1)令y=0x²-5x+4=0(x-4)(x-1)=0x=4或x=1x取1或4时,y的值等于0令y=4x²-5x+4=4x²-5x=0x(x-5)=0x=0或x=5x取0或5时,y的值等于4.(2)x²+2x-1=3-x整理,得x²+3x-4=0(x+4)(x-1)=0x=-4或x=1x取-4或1...