Arrange in descending order.

1.) -3 + y
2.) 2y + y^2 - 6
3.) -m + 3 - m^2
4.) 3b^2 + 2b^3 - 4 - 3b
5.)13 + n^2

To arrange the given expressions in descending order, we need to arrange them from the highest power to the lowest power of the variable and simplify them if necessary. Let's go through each expression step by step:

1.) -3 + y
Since this expression does not have any variable with an exponent, we can consider it as a constant. Therefore, it remains the same.

2.) 2y + y^2 - 6
In this expression, we have a variable with an exponent. Let's rewrite the expression in descending order:
y^2 + 2y - 6

3.) -m + 3 - m^2
Similarly, rearrange the expression in descending order of the variable:
-m^2 - m + 3

4.) 3b^2 + 2b^3 - 4 - 3b
Rearrange the expression in descending order:
2b^3 + 3b^2 - 3b - 4

5.) 13 + n^2
Since n^2 is the highest power of n in this expression, it should come first:
n^2 + 13

Now, here are the expressions arranged in descending order:
1.) -3 + y
2.) y^2 + 2y - 6
3.) -m^2 - m + 3
4.) 2b^3 + 3b^2 - 3b - 4
5.) n^2 + 13