What is the slope of the line passing through # (7,9) ; (-5,-9) #?

1 Answer
Jan 26, 2016

The slope is equal to #2/3#.

Explanation:

You can calculate the slope bij #(Delta y)/(Delta x) = (y_b-y_a)/(x_b-x_a)#.
Let's call the first point #B# and the second one #A#, because #A= (-5,-9)# lays in the left half of the coördinate system, and #B=(7,9)# in the right half.

Okay, #y_b# is the #y#-coördinate of point #B#, so #y_b=7# etc.

Hold in mind that #1--2# is equal to #1+2=3#.
#(Delta y)/(Delta x) = (y_b-y_a)/(x_b-x_a) = (7--5)/(9--9)=(7+5)/(9+9)=12/18=2/3#.