Question

In an ap an = 10-3n find s40

Answer 1

Answer:

I too don't know but thanks for free points

Answer 2

Answer:

Step-by-step explanation:

ANSWER

tn=10-3n

T1 =10-3[1]

   = 10-3

   =7

T2 =10-3[2]

   =10-6

   = 4

d = a2 -a1

  = 4-7

  = -3

Sn = n/2 [ 2a +  [n-1] d

S40= 40/2 [ 2 {7} + {40-1} {-3} ]

     = 20[14+ + 39{-3}]

     = 20 [ 14 + {-117} ]

     = 20 [ -103 ]

     =-2060

hence answer is -2060

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