求满足方程有四个不同根的m值（m值可能不止一个）
f(x)=m|x^2-4x+3| =mx^2-4x+3-m = 0 or x^2-4x+3+m = 0Δ1>0 and Δ2>016-4(3-m)>0 and 16-4(3+m)>04+4m>0 and 4-4m>0m>-1 and m<1-1M ={ m| -1
