MULTIPLE-CHOICE QUESTIONS

If $x+y=13$ and $xy=7$ then $\left(x^2+y^2\right)$ is equal to 

The solid which is not polyhedron is 

If a polyhedron has $12$ vertices and $8$ faces, then the number of edges of the polyhedron is

Which of the following is not a representation of Euler's formula?

A polyhedron has $5$ faces and $9$ edges. The number of vertices is 

Which of these is not a factor of $-21x{y}^2$?

The greatest common factor of the expression, $-5x^3{y}^2,10x{y}^{2}z$ and $15y^2{z}^2$

The greatest common factor of the expression, $35a^3{b}^2{c}^5,-45a^4{b}^3{c}^2$ and $55a^7{b}^5{c}^8$