Question

if Sn = 5n - 2 n2, find Tn​

Answer 1

Answer:

Sn = 5n- 2n²

n= 1

S1= 5 -2 = 3

n= 2

S2 = 10-8 = = 2

n= 3

S3 = 15-18 = -3

tn = tn - tn-1

t1 = S1 -S0 = 3-0 = 3

t2 = S2-S1 = 2-3 = -1

t3 = S3-S2 = -3-2 = -5

common difference

t2-t1 = t3-t2

=> -1-3 = -5-(-1)

=> -4= -4

so common difference d = -4

hence the A.P. is

3, 3-4 = -1, -1-4 =-5

=> 3,-1,-5

Step-by-step explanation:

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