(a+2b)(a-2b)-2(a+2b)
=(a+2b)(a-2b-2)
两张画四个?题错了吧!
4派r+派r2
漏的题为:当X1=1时Y=M,当X2=3时Y=M,所以对称轴是直线X=(X1+X2)/2=2