Question

If sn = n² + 2n, then find first term & common difference?​

Answer 1

Answer:

solution

given condition, $sn=n^{2} +2n$

now

     when n=1,

               $s*1=1^{2} +2*1\\s=1+2\\s=3$

so the first term $t_{1} =3$

     when n=2,

           $s*2=2^{2} +2*2\\2s=4+4\\s=\frac{8}{2}\\s=4$

so the first term $t_{2} =4$

now the common differences= $t_{2}- t_{1} =4-3=1$

                 

Step-by-step explanation:

Answer 2

Answer:

Step-by-step explanation:

here,i am assuming that Sₙ is sum of n terms that u meant.

Sₙ=n² + 2n

ok S₁ (the sum of first term)which is also equal to first term t₁

=(1)²+(2×1)=1+2=3

S₂(the sum of first two terms)=(2)²+(2×2)=4+4=8

so we can find the second term t₂ which is equal to the difference of sum of first two terms and the sum of first term(which is the first term itself)

i.e,S₂-S₁=8-3=5

so t₂=5

so the common difference 'd' =difference of two consecutive terms=t₂-t₁

=5-3=2

so first term t₁=3 and common difference d=2

Hope this helps you

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