PLZ HELP NEED ASAP, much appreciated
1 answer:
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Answer:
x=-7
Step-by-step explanation:
7x2-x=7
7x2=14.
14-x=7
When you finished the last step, you will subtract 14 to both sides.
14-x=7
14-14-x=7-14
this will cancel out the 14 on the left.
And will leave you with:
-x=7-14
7-14 is -7.
and this will get you to
-x=-7
To finish this off, you have to turn the negative x/variable, into a positive x/variable.
So, you will divide both sides of the equation by the same term.
-x = -7
into
and it will be -7.
I hope this helps :)
Answer:
The sum of the first 20 terms is -1440.
Step-by-step explanation:
We want to find the sum of the first 20 terms of the arithmetic sequence:
4, -4, -12, -20...
The sum of an arithmetic sequence is given by:
Where <em>k</em> is the number of terms, <em>a</em> is the initial term, and <em>x</em>_<em>k</em> is the last term.
Since we want to find the sum of the first 20 terms, <em>k</em> = 20.
Our initial term <em>a</em> is 4.
Our last term is also the 20th term as we want the sum of the first 20 terms.
To find the 20th term, we can write an explicit formula for our sequence. The explicit formula for an arithmetic sequence is given by:
Where <em>a</em> is the initial term, <em>d</em> is the common difference, and <em>n</em> is the <em>n</em>th term.
Our initial term is 4. From the sequence, we can see that our common difference is -8 since each subsequent term is eight less than the previous term. Therefore:
Then the last or 20th term is:
Therefore, the sum of the first 20 terms are: