ANSWER:
STEP-BY-STEP EXPLANATION:
We have the following function:
[tex]f(x)=x^4\:-\:2x³\:-\:11x²\:+\:12x\:+\:36[/tex]
We solve the polynomial as follows:
[tex]\begin{gathered} x^4-2x^3-11x^2+12x+36=0 \\ \\ \left(x+2\right)\frac{x^4-2x^3-11x^2+12x+36}{x+2} \\ \\ \begin{matrix}\texttt{\:\:\:-2¦\:\:\:\:1\:\:\:-2\:\:-11\:\:\:12\:\:\:36}\\ \texttt{\:\:\:\:\:¦\underline{\:\:\:\:\:\:\:\:-2\:\:\:\:8\:\:\:\:6\:\:-36}}\\ \texttt{\:\:\:\:\:\:\:\:\:\:1\:\:\:-4\:\:\:-3\:\:\:18\:\:\:\:0}\end{matrix} \\ \\ \frac{x^4-2x^3-11x^2+12x+36}{x+2}=x^3-4x^2-3x+18 \\ \\ \left(x+2\right)\frac{x^3-4x^2-3x+18}{x+2} \\ \\ \begin{matrix}\texttt{\:\:-2¦\:\:\:1\:\:-4\:\:-3\:\:18}\\ \texttt{\:\:\:\:¦\underline{\:\:\:\:\:\:-2\:\:12\:-18}}\\ \texttt{\:\:\:\:\:\:\:\:1\:\:-6\:\:\:9\:\:\:0}\end{matrix} \\ \\ \frac{x^3-4x^2-3x+18}{x+2}=x^2-6x+9 \\ \\ (x+2)(x+2)(x^2-6x+9) \\ \\ (x^2-6x+9)=(x-3)^2 \\ \\ (x+2)^2(x-3)^2=0 \\ \\ x+2=0\rightarrow x=-2 \\ \\ x-3=0\operatorname{\rightarrow}x=3 \end{gathered}[/tex]
