The Sign Inside

A plus inside the brackets moves the graph left, which surprises most people at first. Take y = f(x + 2) with f(x) = x^2. The parent's lowest output comes when f receives 0. Here f receives x + 2, and that is 0 when x is -2. So the vertex is at (-2, 0), two places left.

Follow one more point to see why. On the parent, input 2 gives 4: the point (2, 4). On the new graph, f must receive 2, so x + 2 = 2 and x is 0. The point with height 4 is now (0, 4). The rule adds 2 to x before f sees it, so x has to be 2 smaller to feed f the same number, and smaller x means further left.

So do not guess from the sign. Ask where the inside of the brackets is 0: that is where the vertex goes. f(x + 2) is zero inside at -2, and f(x - 2) at 2.