Question

I'm trying to work out how n(n+1)+n is the same as n squared + 2n

Answer 1

$$\Large \color{red}n(n+1) + n$$
See that red n just outside the parentheses? Distribute it.

Answer 2

Ohhhh, I'm learning algebra for the 1st time. :D So.... red n multiplied by black n is Nsquared. Red n multiplied by 1 is n. Same as Nsquared + 2n. I got there in the end. :D