Question

if the sum of n term of an ap is sn 3n2+7n. find it's first term common difference and s10​

Answer 1

Answer:

First term = 3(1) ²+7(1) =10

sum of first two terms=3(2) ²+7(2) ==26

so second term=26-10=16

common difference=16-10=6

sum of first 10 numbers=10/2(2×10+(10-1) ×6) =1950

Answer 2

Step-by-step explanation:

Sn = 3n² + 7n

therefore S1= 3+7 = 10

we know S1 is the first term

therefore first term is 10

S2= 3(2)² + 7(2) = 12 + 14 = 26

we know Sn- S(n-1) = An

therefore S2-S1 =A2

so second term is 26-10 = 16

common difference = second term - first term

so common difference = 16-10= 6

S10 = 3(10)² + 7(10)

S10 = 300 + 70 = 370

sum of first ten terms is 370

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