比较大小 (1)-3x²+2x+1和-3x²+2x-3 (2)-x+2和-y+2(x<y)
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![比较大小 (1)-3x²+2x+1和-3x²+2x-3 (2)-x+2和-y+2(x<y)](/uploads/image/z/744912-0-2.jpg?t=%E6%AF%94%E8%BE%83%E5%A4%A7%E5%B0%8F+%EF%BC%881%EF%BC%89-3x%26%23178%3B%2B2x%2B1%E5%92%8C-3x%26%23178%3B%2B2x-3+%EF%BC%882%EF%BC%89-x%2B2%E5%92%8C-y%2B2%EF%BC%88x%EF%BC%9Cy%EF%BC%89)
比较大小 (1)-3x²+2x+1和-3x²+2x-3 (2)-x+2和-y+2(x<y)
比较大小 (1)-3x²+2x+1和-3x²+2x-3 (2)-x+2和-y+2(x<y)
比较大小 (1)-3x²+2x+1和-3x²+2x-3 (2)-x+2和-y+2(x<y)
求差比较 如果a-b>0
那么a>b
(1)-3x²+2x+1和-3x²+2x-3
∵(-3x²+2x+1)-(-3x²+2x-3 )
=4>0
∴-3x²+2x+1>-3x²+2x-3
(2)-x+2和-y+2(x<y)
(-x+2)-(-y+2)
=y-x>0
∴)-x+2>-y+2(x<y)