x^4-39x^2+108=0 x²=y
y²-39y+108=0
D=39²-4*108=1089=33²
y1=(39+33)/2=36
y2=(39-33)/2=3
x²=36 x1=6 x2=-6
x²=3 x3=√3 x4=-√3
x^4-39x^2+108=0 x²=y
y²-39y+108=0
D=39²-4*108=1089=33²
y1=(39+33)/2=36
y2=(39-33)/2=3
x²=36 x1=6 x2=-6
x²=3 x3=√3 x4=-√3