El numero es 13 porque 13x3= 39 y 39-9= 30.
Drawing a diagonal means to connect a vertex with another non-adjacent vertex.
So, for each vertex, we have 8-3=5 possible diagonals. This leads to a total of 8*5=40 diagonals.
We have to divide this number by 2 though, because in this way we're counting each diagonal twice (connecting points AB or BA gives the same diagonal).
So, an 8 sided shape has 20 diagonals.
Answer:
i think the answer is x=4
hope it helps
The general term for the sequence is n+2.
4x² - 16 is the algebraic expression that must be added to get the result as 9x²- 2x - 5.
<u>Step-by-step explanation:</u>
The question is asked for the algebraic expression must be added to the sum of 3x²+4x+8 and 2x2−6x+3 to give 9x²- 2x - 5 as the result.
Therefore,
The first step is to find of sum of 3x²+4x+8 and 2x²-6x+3.
To find the sum :
3x²+4x+8
<u>2x²-6x+3 </u>
<u>5x²-2x+11</u>
The sum is 5x²-2x+11.
Now, the second step is to subtract 5x²-2x+11 from the result 9x²- 2x - 5.
9x²- 2x - 5
- <u>(5x²-2x+11)</u>
<u> 4x² -16 </u>
Thus, 4x²-16 is the algebraic expression that must be added with 5x²-2x+11 to get a result of 9x²- 2x - 5.
