Find the equations of the tangents to the given curve that pass through the point (12, 10).

x= 6t^2 + 6

y= 4t^3 + 6

I'm following some example but I get confused after

The answers are:

http://www.webassign.net/cgi-bin/sym...-2x%20%2B%2034

and

http://www.webassign.net/cgi-bin/sym...expr=x%20-%202

I understand that m=1 and that makes x-2. But I dont understand is that at one point it looks like m = -2 which is seen in -2x+34 but I dont see how they got m = -2 can someone explain this please.