Question

plss answer question-11!!!!

Answer 1

Given that,

Sn = 4n − n^2

 

First term, a = S1 = 4(1) − (1)^2 = 4 − 1 = 3

 

 

Sum of first two terms = S2

= 4(2) − (2)^2 = 8 − 4 = 4

Second term, a2 = S2 − S1 = 4 − 3 = 1

d = a2 − a = 1 − 3 = −2

an = a + (n − 1)d

= 3 + (n − 1) (−2)

= 3 − 2n + 2

= 5 − 2n

a10 = 5 − 2(10) = 5 − 20 = −15

Answer 2

hey mate!!

given:

Sn = 4n - n²

so 1) S1 = 4(1) - 1² = 3 ans.

we know that : an = Sn - S(n-1)

an = 4n-n² -{4(n-1) -(n-1)²}

= 4n - n² - 4n + 4 + n²+1-2n

=> an = 5 - 2n

=> a1 = 5 - 2×1 = 3

=> a2 = 5-2(2) = 1

sum of first two terms = a1+a2= 3+1=4 ans

second term is a2= 1

third term(a3) = 5-2(3) = -1

tenth term(a10)= 5-2(10)= -15

so nth term (an) = 5 -2n

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thanks♠