Question

Use the formula to evaluate the series 3-9+27-81+...-ae

Answer 1

Answer:

( -4920)

Step-by-step explanation:

we see that the first term is 3 and the common ratio between the succeeding terms is -3. so to  solve for the sum of the first 8 terms

 Sum = (a1)(1 – r^n) / (1 – r)

and substituting the known terms,we got  

  Sum = (3)(1 – (-3)^8)/(1 - (-3)) = -4920

Then the answer   = ( -4920)