If the sum of n terms off an
a.p. is 3n2 + 5n and its mth term is 164, find the value of m.
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Step-by-step explanation:
Tn=3n²+5n
T1=3(1)²+5(1) =3+5 = 8
T2 = 3(2)² + 5(2) = 12+10 =22
T3 = 3(3)² + 5(3) = 27+15 =42...
A1 = 8
A2= 22-8 =14
A3 = 42-22 =20
hence,the a.p is 8,14,20........
a=8. ,d=14-8=6 ,mth term = 164
Tn = a+(n-1)d
164 = 8 + (m-1).6
164-8 =(m-1).6
156 =(m-1).6
(m-1)=156/6
(m-1) = 26
m=26+1
m=27
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