Question

how many term if the ap 9.17.25........ are needed to make the sum450

Answer 1

Answer:

if AP is 9, 17 , 25

and sum is 450

Step-by-step explanation:

a= 9, d= 8, Sn= 450

Sn= n/2 [ 2a + n - 1 ) d]

450 = n/2 [ 2* 9 + (n - 1) (8)]

450= 4n^2 + 5n

4n^2 + 5n - 450=0

4n^2 - 4on + 45n - 450 = 0

4n (n -10)  + 45 ( n - 10 ) = 0

( n - 10 ) ( 4n  + 45 ) = 0

n = - 45/4  or n = 10

rejecting  n= - 45/4  as a number of term can not be negative

therefore : n = 10

i hope this helps you

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