Find the inverse function of:
$$f(x)=\frac{3x+1}{2-7x}$$
I did the question and when I checked my answer with the key it was wrong, can someone please show me how to properly do this problem? I followed all the steps and the answer I came up with was:
$$\frac{2x-1}{7x+3}$$
but the correct answer is supposed to be:
$$\frac{-(1-2x)}{7x-3}$$