Question

Sum of ‘n’ terms of an arithmetic sequence 3n2+4n a. Find the first term? b. Find the sum of 20 terms of this arithmetic sequence?

Answer 1

$\huge\bigstar\purple{To\:find}$

$\bf{first \: term}$

$\huge\sf\green{given}$

• 3n^2+4n

SoluTionN:

{a}

3(1)^2+4(1)

9+4=13

{b}

Formula :[S=n/2(2a+(n-1)d]

here n(number of terms) =20

a(first term)=13

d(common distances) =second term-first

term=[3(2)^2+4(2)]-[13]=[12+8]-[13]=20-13

=7

S=10(26+19*7)=10(26+133)=10(159)=1590

❤hope it help you

mark brainleast

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