i swear im right !

Which of the follwoing is equivalent to
5
singma 3n +2 ?
3

i did 3(3)+2 +3(4)+2 +3(5)+2 and got 42. my teacher says this is incorrect !

Question

i swear im right !  

Which of the follwoing is equivalent to 
    5
singma 3n +2 ?
     3                                                     

i did 3(3)+2 +3(4)+2 +3(5)+2 and got 42. my teacher says this is incorrect !

ganeshie8 · Answer

pls post the full q... 

n varies from wat to wat  ?

anonymous · Answer

n=3 sorry

unklerhaukus · Answer

$$\sum\limits_{n=3}^53n+2$$$$=(3(3)+2) +(3(4)+2) +(3(5)+2)$$$$=(9+2)+(12+2)+(15+2)$$$$=9+12+15+3\times2$$$$=21+15+6$$$$=21+21$$$$=42$$

anonymous · Answer

$$\sum_3^5(3n+2)$$?

unklerhaukus · Answer

is the two is definitely in the sum ?

anonymous · Answer

unkle thats what i did !

unklerhaukus · Answer

maybe there is another method that the teacher is looking for,

anonymous · Answer

i dont know any other methods we didnt learn any other methods. ...

anonymous · Answer

don't give it another thought, you have three numbers to add and you did it correctly
either the teacher is wrong, (it happens) or there is a typo somewhere

unklerhaukus · Answer

$$\sum\limits_{n=3}^5(3n+2)$$$$=3\sum\limits_{n=3}^5n+\sum\limits_{n=3}^52$$$$=3(3+4+5)+(2+2+2)$$$$=3(12)+6$$$$=36+6$$$$=42$$

mathmate · Answer

...unless the "+2" at the end does not belong to the summation if what you posted is part of a longer expression.