Question 1205679
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the nth term of a sequence is {{{highlight(cross(denoted))}}} {{{highlight(cross(by))}}} 3n(2n-1). 
Find the sum of the first 5 terms
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<pre>
n= 1:  {{{a[1]}}} = 3*1*(2*1-1) = 3*1 = 3

n= 2:  {{{a[2]}}} = 3*2*(2*2-1) = 6*3 = 18

n= 3:  {{{a[3]}}} = 3*3*(2*3-1) = 9*5 = 45

n= 4:  {{{a[4]}}} = 3*4*(2*4-1) = 12*7 = 84

n= 5:  {{{a[5]}}} = 3*5*(2*5-1) = 15*9 = 135


Thus you just know the first five terms.
To find their sum, add these 5 numbers.


You should get the <U>ANSWER</U> 285.
</pre>

Solved.


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In whole, the task is as simple as a cucumber.


The words in the condition, &nbsp;crossed by red, &nbsp;are excessive and unnecessary.


They do not make the problem's formulation better.
In opposite, &nbsp;they make it worst, &nbsp;so I recommend to remove them.