if-1-x-1-x-2-1-x-128-r-0-n-x-r-then-find-n-

Question Number 96318 by M±th+et+s last updated on 31/May/20

i f

(1 + x) (1 + x^{2}) \dots . . (1 + x^{128}) = \underset{r = 0}{\sum^{n}} x^{r}

t h e n f i n d n

Commented by mr W last updated on 31/May/20

n = 1 + 2 + 3 + \dots + 128 = \frac{128 \times 129}{2} = 8256

Commented by M±th+et+s last updated on 31/May/20

t h a n k s s i r

Commented by mr W last updated on 31/May/20

b u t

(1 + x) (1 + x^{2}) \dots . . (1 + x^{128}) = \underset{r = 0}{\sum^{n}} a_{r} x^{r} \neq \underset{r = 0}{\sum^{n}} x^{r}

Commented by M±th+et+s last updated on 31/May/20

y e s s o r r y i t s (1 + x) (1 + x^{2}) (1 + x^{4}) \dots . (1 + x^{128})