Find the rule 8.8 4.4 2.2 ()（ Find the law 8.8 4.4 2.2 ( ) ( ) ( ) How do you write it?

Find the rule 8.8 4.4 2.2 ()（ Find the law 8.8 4.4 2.2 ( ) ( ) ( ) How do you write it?

Friends, should be 1.1, 0.55, 0.2775, hope to adopt!

1 / 3, - 2 / 15, 3 / 35, - 4 / 63

The molecules are 1, - 2,3, - 4, and the next one is 5
The denominator is 1 * 3, 3 * 5, 5 * 7, 7 * 9, and the next is 9 * 11 = 99
The next one is 5 / 99
The nth is (- 1) ^ (n-1) * n / ((2n-1) * (2n + 1))

Find the rules and write the appropriate numbers on the horizontal line: 1 / 3, - 2 / 15, 3 / 35 - 4 / 63
What's in the back

5 out of 99
The nth term is (- 1) ^ (n + 1) * n / ((2n-1) * (2n + 1))