3(х²+5х+1)²+2х²+10х=3,
3(х²+5х+1)²+2х²+10х-3=0,
3(х²+5х+1)²+2х²+10х+2-5=0,
3(х²+5х+1)²+2(х²+5х+1)-5=0,
х²+5х+1=t,
3t^2+2t-5=0,
D₁=16,
t₁=-⁵/₃,
t₂=1;
х²+5х+1=-⁵/₃,
3х²+15х+3=-5,
3х²+15х+8=0,
D=129,
x₁=(-15-√129)/6,
x₂=(-15+√129)/6;
х²+5х+1=1,
х²+5х=0,
x(x+5)=0,
x₃=0,
x+5=0, x₄=-5.