Question

The nth term of an arithmetic sequence is 5-6n Find the sum of its 1st n terms ​

Answer 1

Answer:

Step-by-step explanation:

a1=5-6

  = -1

a2= 5-12

   =-7

d=-7-(-1)

  =-6

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

  = n/2[-2-6n+6]

  =n/2[4-6n]

  =n(2-3n)

  = 2n-3n^2