The first and second term of a linear sequence (A.p) are 3 and 8 respectively. Determine the least number of terms of the A.P that must be added so that the sum is greater than 250.​

Respuesta :

We are to find the number of terms in the AP that has a sum greater than 250

The number of teams in the AP which has a sum greater than 250 is at least 11 terms

First term, a = 3

second term, a + d = 8

so

common difference, d = 8-3

= 5

let

n = number of terms in the AP

The sum of n terms is 250

Sum = n/2{2a + (n - 1)d}

250 = n/2{2*3 + (n-1)5 }

250 = n/2{6 + 5n - 5}

250 = n/2(1 + 5n)

500 = n + 5n²

5n² + n - 500 = 0

Solve quadratically using formula

n = -b ± √b² - 4ac / 2a

= -1 ± √1² - 4(5)(-500) / 2(5)

= -1 ± √1 - (-10000) / 10

= -1 ± √1 + 10000 / 10

= -1 ± √10001 / 10

= -1 + √10001 / 10 or -1 - √10001 / 10

= -1/10 + √10001/10

or

-1/10 - √10001 / 20

= 9.9005 or -10.1005

The value of n must be positive and a whole value

Therefore,

n = 9.9005

Approximately, n = 10

The number of teams in the AP which has a sum greater than 250 is at least 11 terms

Read more:

https://brainly.com/question/24321873

ACCESS MORE