bear in mind that, a "solution" so-called, or a zero, or a root, is really just an x-intercept of the graph, namely, where does the graph touch the x-axis? that's a zero/root/solution/x-intercept.
now, about those two lads above, check the picture below.
notice, that, the horizontal line, by definition will never touch the x-axis, whilst the other one does, at x = 2.