Question

How many terms of an ap 9 17 25 ....Must be taken to get a sum of 450?

Answer 1

Answer:

10 terms

Step-by-step explanation:

Given:

a=9

d=8

Sum of n terms=450

450=n/2(2a+((n-1)d))

      =n/2(18+8n-8)

      =n/2(10+8n)

      =n(5+4n)

      =>4n²+5n-450=0

      =>4n²-40n+45n-450=0

      =>4n(n-10)+45(n-10)=0

      =>(4n+45)(n-10)=0

     ∴n=10,-45/4

As number of terms cannot be negative, n=10.