If you want to shift the graph of a function <em>horizontally left</em>, then you <em>add</em> some amount to the x-value. If a <em>horizontal right</em> shift is needed, then you <em>subtract</em> from the x-value.
Furthermore, if you wish to move your graph <em>vertically up</em>, then <em>add</em> to the y-value (the function itself). And <em>subtract</em> from it for a <em>vertically down</em> shift.
Now, we need a <em>horizontal </em><u><em>3</em></u><em> unit left</em> shift. That means we <em>add </em><u><em>3</em></u> to the x-value, without touching the function itself. The function is , hence the shifted function is .