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Mathematics 16 Online
OpenStudy (anonymous):

CAN SOMEONE PLEASE HELP i only need help with the second one in the picture.

OpenStudy (anonymous):

OpenStudy (anonymous):

didnt you have tons of replies for this one?

OpenStudy (anonymous):

nope.

OpenStudy (helder_edwin):

u mean B. right?

OpenStudy (anonymous):

yeah i did the first one already

OpenStudy (helder_edwin):

there r 8 terms. the first term is for n=1 so it is \[ \frac{2\cdot1}{3}=\frac{2}{3}. \] the last term is for n=8 so it is \[ \frac{2\cdot8}{3}=\frac{16}{3} \]

OpenStudy (anonymous):

so the amount of terms is always just the number on top?

OpenStudy (helder_edwin):

for the last part \[\large \sum_{n=1}^8\frac{2n}{3}=\frac{2}{3}\sum_{n=1}^8n= \frac{2}{3}\cdot\frac{8(8+1)}{2}=\frac{8\cdot9}{3}=24 \]

OpenStudy (helder_edwin):

NO. if u have \[\large \sum_{n=a}^A \] then the number of terms is A-a+1

OpenStudy (anonymous):

thank you so much

OpenStudy (helder_edwin):

u r welcome

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