Solution
= Solution
The <geometric realization of a simplicial complex> consists of the filled triangle $\langle v_1,v_2,v_3\rangle$ together with the two extra edges $\langle v_1,v_4\rangle$ and $\langle v_2,v_4\rangle$. Thus the triangle on $v_1,v_2,v_4$ has only its boundary:
\Image[/past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2020/ii/paper-3-simplicial-complex.png]
{title=The vertices, edges and faces of a <simplicial complex>}