Using pythagoras a^2 + b^2 = c^2
8^2 + 3^2 = c^2
64 + 9 = 73
The square root of 73 is 8.54
So the length of the diagonals are 8.54cm
9,2.5,-4,-10.5,-17
Let's find the difference between two consecutive terms
2.5 - 9 = -6.5
-4 - 2.5 = -6.5
-10.5 - (-4) = -6.5
-17 -(-10.5) = -6.5
We can see that the common difference is -6.5
-6.5 is the common difference between successive terms in the sequence 9,2.5,-4,-10.5,-17
the common difference is negative because we subtract 6.5 to get the next term.
You would change it because it is the simplest answer