Chemistry help?

Both CO₂ and CCl₄ are both symmetrical molecules.

Refer to the diagram below which shows the dipole moments (arrows in red) in CO₂ and CCl₄ molecules.
https://c1.staticflickr.com/3/2950/33889971110_3d9eb8cf07_o.jpg

In each molecule of CO₂ and CCl₄, the dipole moments cancel other and thus the net dipole moment of the molecule is zero. Hence, the molecules of CO₂ and CCl₄ are non-polar.

Their molecular shapes.