$1, -3, -7, -11, ...\ \ \ \ \rightarrow\ \ \ the\ arithmetic\ sequence\\\\the\ difference\ of\ the\ sequence\ is\ \ \ \ d=-3-1=-4\\\\the\ sum:\ \ \ \ S_n= \frac{\big{2\cdot a_1+(n-1)\cdot d}}{\big{2}} \cdot n\\\\\\S_8= \frac{\big{2\cdot1+(8-1)\cdot(-4)}}{\big{2}} \cdot8=(2-28)\cdot4=-26\cdot4=-104\\\\Ans.\ The\ sum\ is\ -104.$

4 0

3 years ago

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Esteban is reading a book with 16 pages. He has read 9 pages so far. How many pages does Esteban have left to read? Write two eq

Zielflug [23.3K]

Answer:

7 pages

Step-by-step explanation:

Given the total number of pages in the book are 16

The number of pages esteban already read are 9

Let the number of pages left out to read be x

Total number of pages = number of pages read + number of pages to be read

16=9+x

x=16-9

x=7 pages

Therefore There are 7 pages left out to be read.

8 0

3 years ago