Question

The sum of the first four terms in an arithmetic progression is -18 and the sum of the first six terms is -9. Find the sum of the first ten terms.​

Answer 1

Answer:

45

Step-by-step explanation:

Let the first term be a and the common difference be d.

So -18=4a+6d and -9=6a+15d. Solving this we get a=-9 and d=3.

So the sum of first 10 terms is 5*(2*(-9)+9*(3))=45