By the first term of the given function 7lx - 3l you can notice that there is a translation 3 units to the right of the pattern function lxl. This allows one to conclude that the x-coordinate of the vertex is 3.
Now, for such a value of x the function value is 7l3 - 3l - 2 = -2. Then, the y-coordinate of the vertex is -2.
Hence, the vertex of the function is (3,-2)
