Question

if 11+9+7....n terms = -13 then the value of n is ​

Answer 1

Step-by-step explanation:

a = 11, d = - 2 and Sn = -13

to find n

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

-13 = n/2 [ 22 + (n - 1) × -2 ]

-26 = n [ 22 - 2n + 2 ]

-26 = n [ 24 - 2n ]

-26 = 24n - 2n²

=> 2n² - 24n - 26 = 0

=> n² - 12n - 13 = 0

=> n² - 13n + n - 13 = 0

=> n( n - 13) + 1(n - 13) = 0

=> (n - 13)(n + 1) = 0

=> n - 13 = 0 => n = 13 √

=> n + 1 = 0 => n = - 1 ×

therefore number of terms n = 13

Answer 2

Answer:

That's it my friend...