Change of variables in a partial devivative

[jason12345]

If I have the equation and function f_1(x_1,x_2,x_3,...,x_n) = 0,\qquad x_1 = g_1(y_1, y_2, y_3,...,y_m) then what is \frac {\partial f_1}{\partial x_1} in terms of \frac{\partial g_1}{\partial y_i}?