If T n -3 n -1 of an A-P- thenA- a -2B- d -3C- T 5-15D- S 3-15

The correct options are A a=2 B d=3 D S_3=15Given : T_n=3n 1 Now, a = T_1=3×1 1=2 ⋯(i) a+d=T_2=3×2 1=5 ⋯(ii) a+2d=T_3=3×3 1=8 ⋯(iii) a+3d=T_4=3×4 1=11 ...

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Standard XII

Mathematics

Series

If T n =3 n -...

Question

If $T_{n} = 3 n - 1$ of an A.P., then

a = 2

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d = 3

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T_{5} = 15

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S_{3} = 15

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Solution

The correct options are
A $a = 2$
B $d = 3$
D $S_{3} = 15$
Given : $T_{n} = 3 n - 1$
Now,
$a = T_{1} = 3 \times 1 - 1 = 2 \dots (i) a + d = T_{2} = 3 \times 2 - 1 = 5 \dots (i i) a + 2 d = T_{3} = 3 \times 3 - 1 = 8 \dots (i i i) a + 3 d = T_{4} = 3 \times 4 - 1 = 11 \dots (i v)$
Therefore, $a = 2, d = 3$
Now,
$S_{3} = T_{1} + T_{2} + T_{3} ∴ S_{3} = 2 + 5 + 8 = 15$

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If Tn=3n−1 of an A.P., then

The correct options are A a=2 B d=3 D S3=15Given : Tn=3n−1 Now, a=T1=3×1−1=2 ⋯(i)a+d=T2=3×2−1=5 ⋯(ii)a+2d=T3=3×3−1=8 ⋯(iii)a+3d=T4=3×4−1=11 ⋯(iv) Therefore, a=2,d=3 Now, S3=T1+T2+T3∴S3=2+5+8=15

If $T_{n} = 3 n - 1$ of an A.P., then