Question

Find the common difference of an AP if sum to n terms be 7n²-6n??????

Answer 1

Sn=n/2[2a+(n-1) d]=7n²-6n

2an/2+ nd(n-1)/2= 7n²-6n

2an+ nd(n-1)= 14n²-12n

n(2a+ (n-1)d)=14n²-12n

2a+(n-1)d=2(7n-6)

(n-1)d=2(7n-6)- 2a

d=(2(7n-6-a))/ (n-1)