(x²+12x+11)(x²+12x+36)+24≤0
x²+12x+11=a
a(a+25)+24≤0
a²+25a+24≤0
(a+24)(a+1)≤0
a=-24 U a=-1
+ _ +
-----------[-24]---------------[-1]-----------------------
-24≤a≤-1
{x²+12x+11≥-24⇒x²+12+35≥0⇒x∈R,D<0<br>{x²+12x+11≤-1⇒x²+12x+12≤0
D=144-48=96
x1=(-12-4√6)/2=-6-2√6
x2=-6+2√6
x∈[-6-2√6;-6+2√6]