While doing some work, I came across a problem in my high school textbook that asked me to differentiate
$$y = (2x+1)^2,$$
which I know how to do using chain rule. But the problem is that this problem was in the first section in the chapter of derivatives -- the chain rule isn't taught until later. Which leaves me wondering if there's another, simpler method of deriving this problem. I feel like it's really simple, but I can't figure it out.