Another way to do this is to realize the 4t from the y equation and the 2t from the x equation is actually rise over run: 4/2 = 2. You have a point on this line given by the 3 in the x equation (3,y), and the -5 in the y equation (3,-5). You can use this point to find b by substituting : y=mx + b (put in your m that you found from rise/run)---> y=2x + b (put in your point to solve for b) -5=6 + b, b=-11. Rewrite your line equation using m and b: y=2x -11. Or in standard form: 2x-y-11=0. Saves you from the fractions. Mind you if your rise/run ends up being a fraction, you're back to solving fractions.
Yes. You should.... most of the concepts link to previous concepts. All of math is like that, if you skip it can make it really hard to understand what you are doing, and why you are doing it.
Again a faster method at 22:10. Anything is parallel if they have the same m...m is right in the vector equation. In line 2 the rise is 12, the run is 3, so m=4. In line 1, the rise is 4, the run is 2 , so m=2. Not parallel. You should learn the scalar trick for 3 dimensional vectors, so thats why its taught this way.
