Analysing the Question:
We are given the following equations:
x - y = 4
x + y = 9
writing these equations in slope-intercept form
y = x - 4
y = -x + 9
the general form of the slope-intercept equation is : y = mx + b (where m is the slope and b is the y-intercept)
Hence, we can say that the for Equation 1:
Slope = 1
y-intercept = -4
For equation 2:
Slope = -1
y-intercept = 9
Finding if the lines are Perpendicular, parallel or neither
If the slope of the lines is equal, the lines are parallel
If the slope of the lines is the additive inverse (negative) of each other, the lines are perpendicular
Since the slopes of the 2 lines are the additive inverse (negative) of each other, the lines are perpendicular [slope 1 = 1 , slope 2 = -1]