Question

Se 1+ (1+a) + (1+2a) +...(1+6a) =49 , Qual valor de a

Answer 1

1+ (1+a) + (1+2a) +...(1+6a) =49
1+(1+a)+(1+2a)+(1+3a)+(1+4a)+(1+5a)+(1+6a)=49
7+21a=49
21a=49-7
21a=42
a=42/21
a=2