Yep, a clerical error. Here is a bit more step by step with what I came out with:
Basically I started with your second line (can't read the first).
I subtracted both sides to gather like terms (in this case, the dx / dy on one side, everything else on the other).
dx/dy were on both parts of the left side so I simply moved the multiply operation to the left of the parenthesis.
Divide both sides by what is in the parenthesis.
Now, a little cleanup on the right side of the equals sign and done.
Thanks for the moment of math! Do I get a gold star?
