Remark
Perpendicular slopes are found by using the formula m1*m2 = - 1. That is followed by using the given point to determine the y intercept.
Solution
Step One
Find the slope of the new line
m1 = - 1/3
m2 = ??
m1 * m2 = - 1
(-1/3) * m2 = - 1
You could continue by changing (-1/3) to a decimal.
(-0.3333333333) * m2 = -1 Now divide by the decimal
m2 = - 1/ (-0.3333333333)
m2 = 3 which is what my calculator tells me the answer is.
Step Two
So far what you have is
y = 3x + b
Use the point (-3, -7) to get the y intercept.
-7 = 3(-3) + b
b - 9 = - 7
b = -7 + 9
b = 2
y = 3x + 2 Answer
Graph
The graph shown below is both lines plotted in desmos. The red line is y = 3x + 2 which is perpendicular to the given graph y = (-1/3)x +5 which is in blue.
The green dot is the point (-3 , - 7)
