Answer:
21-9 = 12
Step-by-step explanation:
I don't know if this is the correct sentence you are looking for though but i hope it helps
The net cannot be folded to form a pyramid because the faces that are not a base are not all triangles
If you fold this net up, you will get a triangular prism, NOT A PYRAMID.
A pyramid can have ANY polygon as its base, as long as all the other rest of the shapes are triangles.
Depending on the base, the number of triangles in a net of a pyramid must match the number of sides its particular base has.
For example, if you have a square pyramid turned into a net:
The base is a square (4 sides)
There should be 4 triangles on each side.
Because a pyramid is where all the triangles must meet up at a point.
Hope this helps!
Answer:

Step-by-step explanation:
Given the equation of the circle: 
We wish to express it in a Standard form:
We begin by re-arranging:

Next, divide the coefficient of x by 2, square it and add it to both sides.
Do the same for y.

Next, we factorize

This is the standard form.
Answer:
The correct answer is - 900
Step-by-step explanation:
A palindrome is a positive integer that is same whether read from left to right or from right to left. For example, 123321 palindromes.
An n-digit palindrome is determined from the first n/2 digits if n is even, and from the first n+1/2 digits if n is odd.
Therefore, if n is even, there are 9×10⁽n⁻²/²⁾ palindromes; and if n is odd, there are 9×10⁽n₋²/²⁾ palindromes. where n is number of digits.
For n=5 , there are 9×10²=900 palindromes