Answer:
-62.5008
Explanation:
The terms form a geometric sequence with first term -75 and common ratio -1/5. The sum of n terms of such a sequence is...
Sn = a1(1 -r^n)/(1 -r)
For the values of a1, r, and n, this sum is ...
S7 = -75(1 -(-1/5)^7)/(1 -(-1/5)) = -75(1 +1/78125)/(1 +1/5)
= -75(13021/15625) = -62 313/625
= -62.5008
The sum of the first 7 terms of the sequence is -62.5008.