Notice that, since B is the center of dilation, B'=B. Furthermore, is a dilation all the distances are enlarged by a factor equal to the dilation factor; thus,
[tex]\Rightarrow B^{\prime}C^{\prime}=3\cdot BC[/tex]Calculate BC using the formula below,
[tex]\begin{gathered} P_1=(x_1,y_1),P_2=(x_2,y_2)_{} \\ \Rightarrow\text{distance}(P_1,P_2)=\sqrt[]{(x_1-x_2)^2+(y_1-y_2_{})^2} \end{gathered}[/tex]Therefore,
[tex]\Rightarrow\text{distance}(BC)=\sqrt[]{(4-1)^2+(8-(-2))^2}=\sqrt[]{9+100}=\sqrt[]{109}[/tex]Hence,
[tex]\begin{gathered} \Rightarrow B^{\prime}C^{\prime}=3\sqrt[]{109}=31.320919\ldots \\ \Rightarrow B^{\prime}C^{\prime}\approx31.32 \end{gathered}[/tex]The answer is B'C'=31.32