Question

What is the 9th term in the sequence -1,4,-9,16, -25,​

Answer 1

Explanation:

Wow! There are 2 things going on here, so let's go step by step.

The first thing to notice is that the numbers are going negative, positive, negative, positive. Odd-numbered terms are negative while even-numbered terms are positive. Since 9 is odd number, we know the answer must be negative.

Secondly, the 1, 4, 9, 16 sequence is called the square numbers. They are 1 x 1, 2 x 2, 3 x 3, 4 x 4, etc. The 9th term will be 9 x 9 ( ignoring the negative).

Adding the first point with the second, we get (-81) { negative eighty-one }

Hope this helps.