What is the sum of the first 7 terms of this sequence? -4 + 8 - 16 + 32 -...

If the sum of the first n terms of an A.P. is 4n-n^(2) what is the first term? What is the sum of the first two terms? What is the second term? Find the 3rd, 10th, and the nth terms.

Write first three terms of the sequence a_n=(n-3)/(4) .

Find the sum of the products of the corresponding terms of the sequences 2, 4, 8, 16, 32 and 128 , 32 , 8 , 2 1/2

If the first four terms of an arithmetic sequence are a,2a,b and (a-6-b) for some numbers a and b, find the sum of the first 100 terms of the sequence.

The ratio of 11th term to 18th term of an AP is 2:3. Find the ratio of 5th term to the 21st term, also the ratio of the sum of the first 5 terms to the sum of the first 21 terms.

All the terms of an AP are natural numbers and the sum of the first 20 terms is greater than 1072 and lss than 1162.If the sixth term is 32, then

Find the sum of first n terms and the sum of first 5 terms of the geometric series 1+ 2/3 +4/9 +............

If the sum of first p terms of an A.P is equal to the sum of the first q terms , then find the first (p+q) terms .