|4x²-5x+9|-4|x²+2x+2|+3x+7 4x²-5x+9=4（x²-5x/4）+9=4（x-5/8）²+9-25/16＞0可以直接去绝对值
=4x²-5x+9-4x²-8x-8+3x+7 x²+2x+2=（x+1)²+1＞0可以直接去绝对值
=4x²-4x²-5x-8x+3x+9-8+7
=-10x+8
当x=1999
-10x+8
=-19990+8
=-19982