MR-250. problem
x2-4x2-11=x-1
x2-4x2-11=x-1 , 4x2-11>0
4x2>11,  x2>114 , x>112 , x<-112
x2-4x2-112=x-12
x2-4x2-11=x2-2x+1
x2-x2+2x-1=4x2-11
2x-1=4x2-11
2x-12=4x2-112
4x2-4x+1=4x2-11
4x2-4x2=4x-1-11
0=4x-12
12=4x
x=3>112=1,658
x=3
x=3