3 dimensional shapes
What about them? Do you need examples? A sphere is one. You can think of others.
3D shapes are figures that pop out. Like for example, if you saw an airplane fly by your're seeing it in 3D. But if you see an airplane on a piece of paper drawn by a third grader it is not 3D because it doesn't look real, it's just on paper.
a sphere is a 3D shape so is a triangular prism and so forth.
a sphere is a 3D shape so is a triangular prism and so forth.
sum the polynomials 2x^2-3x-4,2x-5 and 3x^3+2x^2-6
Dodecahedron
To sum the polynomials 2x^2-3x-4, 2x-5, and 3x^3+2x^2-6, you simply need to combine like terms.
Start by gathering all the terms with the same power of x together.
In this case, we have:
(3x^3) + (2x^2 + 2x^2) + (-3x) + (2x) + (-4 - 5 - 6)
After combining like terms, we get:
(3x^3) + (4x^2) + (-x) + (-15)
So, the sum of the given polynomials is 3x^3 + 4x^2 - x - 15.
Now, moving on to the second part of your question, a dodecahedron is a 3-dimensional shape. It is a polyhedron with 12 faces, each being a regular pentagon. The dodecahedron has 20 vertices and 30 edges. It is one of the five Platonic solids, which are regular, convex polyhedra.