2x-x³≥0⇒x(√2-x)(√2+x)≥0
x=0 x=√2 x=-√2
+ _ + _
--------[-√2]----------[0]------------[√2]----------------
x≤-√2 U 0≤x≤√2
x^4-3x²+1≠0
x²=a
a²-3a+1≠0
D=9-4=5
a1≠(3-√5)/2 ⇒x²≠(3-√5)/2
a2≠(3+√5)2⇒x²≠(3+√5)/2 ⇒x≠+-√((3+√5)/2)
x∈(-∞;-√((3+√5)/2)) U (-√((3+√5)/2);-√2] U [0;√2]