the sum of the first n terms of an ap is give by 3n²-4ndetermine the apand the 12th term
Answers
Answered by
1
Answer:
67
Step-by-step explanation:
given Sn=3n²-4n
since, an=Sn - S(n-1)
=3n²-4n-[3(n-1)²-4(n-1)]
=3n²-4n-3n²-3+6n+4n-4
=>an=6n-7
=>a12=6*12-7
=>a12=65
Answered by
0
Answer:
65
Step-by-step explanation:
t1=S1=3×1×1-4×1=3-4=-1
S2=3×2×2-4×2=12-8=4
t2=S2-S1=4-(-1)= 4+1=5
d=t2-t1=5-(-1)=5+1=6
t12=a+(n-1)d=(-1)+(12-1)6=-1+11×6
-1+66=65. Answer
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