△>=0
4m²+4m+1-4m²+16m-16>=0
20m>=15
m>=3/4
x=0
0+0+m²-4m+4=0
(m-2)²=0
m=2
x=-1
1-2m-1+m²-4m+4=0
m²-6m+4=0
m=3±√5