Question

The first term of arithmetic sequence is 1 and the sum of the the first four terms is

100..find the first four terms?​

Answer 1

−100

a,2a,b,(a−6−b),.... forms an arithmetic progression

Common difference d=a2−a1=2a−a=ad=a3−a2=b−2a

a=b−2a3a=b(1)a4=a+3d(a−6−b)=a+3a=4aa−6−b=4afrom(1)a−6−3a=4a−6=6a

a=−1 and d=−1

a100=a+99d=a+99a=100aa100=−100