①(x-1)²-4=21
(x-1)²=25
x-1=±5
∴x₁=6
x₂=-4

②(x-0.6)³=0.064
x-0.6=0.4
x=1

③-100(x-1)²=(-4)³
-100(x-1)²=-64
(x-1)²=64/100
x-1=±8/10
∴x₁=1/5
x₂=9/5