а) x³-4x²=0
x²*(x-4)=0
x²=0
x-4=0
x=0
x=4
x₁=0, x₂=4
б) x⁴-11²+18=0
t²-11t+18=0
t=2
t=9
x²=2
x²=9
x=-√2
x=√2
x=-3
x=3
x₁=-3, x₂=-√2, x₃=√2, x₄=3
