Sn=A1(1-r^n)/(1-r) Sum of a finite geometric series formula We know the sum, number of terms and rate, so you plug those in. -255=A1(1-(-4)^4))/(1-(-4) -255=A1(1-256)/5 -255=A1(-255)/5 -1275=A1(-255) 5=A1
Hope this helped! Let me know if you have any questions.
