Question

Find the sum of first 30 term of an AP whose nth term is 2-3n

Answer 1

$\huge\mathfrak{Solution:}$

Given tn=2-3n

t1=-1

t30=2-3 (30)=-88

sum of 30 term=30/2{ (-1)+(-88)}

=15x (-89)

$\huge\boxed{=15x (-89)}$

Answer 2

Step-by-step explanation:

$heloo... \\ \\ its \: nth \: term \: is \: 2 - 3n \\ \\ so \: Tn \: will \: be = > \\ \\ tn = 2 - 3n \\ \\ lets \: find \: first \: term = > \\ put \: n = 1 \\ T1 = 2-3(1) \\ T1 = -1 \: T2 = 2-3(2) \\ T2 = -4 \\ from \: here \: we \: got \: d \: as \: -3 \\ S30 = n/2 (2a +(n-1)d) \\ S30 = 15(-2+87) \\ S30 = 15×85 \\ S30 = 1275 \\ \\ hope \: it \: helps \: uh!!$