f * g means exactly that.
Which is that you should multiply the definitions of the functions.
(x+7)(1/x-13) = x/x-13 + 7/x-13 = x+7/x-13
x+7/x-13
The domain of this function, is x<13 and x>13.
But not 13. Because 13-13 = 0
And it is not legal to divide a number by 0.
Hence, f*g(13) is not defined.
