How do you use sigma notation to write the sum for #[1-(1/6)^2]+[1-(2/6)^2]+...+[1-(6/6)^2]#?
If you look at the expression, the only thing that changes for each term is the number in red:
It starts from one and is incremented by one until it reaches 6. Everything else stays the same. We just need to substitute the number that is changing by a variable: