A) \[-10\]
B) \[-7\]
C) \[+7\]
D) \[+10\]
Correct Answer: B
Solution :
\[{{a}_{4}}={{a}_{1}}+(4-1)\times d\] \[14={{a}_{1}}+3d\] \[\Rightarrow \] \[{{a}_{1}}=14-3d\] ?(i) \[70={{a}_{1}}+11d\] ?(ii) After putting the value of a, in Eq. (ii), we get \[14-3d+11d=70\] \[\Rightarrow \] \[8d=70-14\]\[\Rightarrow \]\[d=7\] \[\therefore \] \[{{a}_{1}}=14-21=-7\]You need to login to perform this action.
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