Straight lines

Questions are straightforward. The main problem should be about the concepts only. So, let's recall the concepts one by one below.


Slope can be analyzed from two perspectives, the sign and the value (absolute value).

Also, lines can be cut into parts and coordinates of points can be found according to the ratios. 口訣: 乘對面

Some reminders

Equation of straight line: y = mx + c

slope = m

y-intercept = c

Another form of equation of straight line: ax + by + c = 0

slope = -a/b

x-intercept = -c/a (not recommand to recite, just sub y=0) 

y-intercept = -c/b (not recommand to recite, just sub x=0)

You can change the given equation to either form if you do not want to recite too many formulas.