A) 382
B) \[-490\]
C) 420
D) \[-382\]
Correct Answer: B
Solution :
We have. \[{{T}_{n}}=(7-3n)\] First term, \[{{T}_{1}}=(7-3\times 1)=4\] Second term, \[{{T}_{2}}=7-3\times 2=1\] Third term, \[{{T}_{3}}=7-3\times 2=-2\] \[\therefore \] Series is \[4,1,-2,\] .......... and common difference \[=-3\] Sum of first 20 terms \[({{S}_{20}})\] \[=\frac{20}{2}[2\times 4+(20-1)\,(-3)]=10\,[8-57]=-490\]You need to login to perform this action.
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