Question

please solve the 3rd q.

step by step explanation plz

Answer 1

Answer:

s=n/2* (-2-6(n-1))

Step-by-step explanation:

a1=5-6= -1

a2=5-12= -7

d=a2-a1= -7-(-1) = -6

s=n/2 * (2(-1))+(n-1)(-6))

s=n/2* (-2-6(n-1))