the formula is [tex] \frac{a_1(1-r^n)}{1-r} [/tex] a1=first term n=which term r=common ratio we see the common ratio is -2 frs term is 1 and we go to 10th term so n=10
[tex] \frac{1(1-(-2)^{10})}{1-(-2)} [/tex] [tex] \frac{1(1-1024)}{1+2} [/tex] [tex] \frac{1(-1023)}{3} [/tex] -341 the sum is -341
