Find the third element of a geometric sequence who fifth element is 81 and whose ninth element is 16. Help please!
You should have been given the formula for finding the nth term of a geometric sequence.
= common ratio
Your first element ( ) will be 81.
because there are five elements in all between the 5th element and the 9th element, inclusive.
Now that you have found the common ratio, substitute back into the original formula and solve for .
This time there are 3 elements from the 3rd to the 5th elements, inclusive. So,