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Find the equation of the line perpendicular to the

given line through the point (1,9). y=1/3x+5

2 Answers

4 votes
No clue I have no idea what it is but this is for the profile
User Oskuro
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2 votes

Slope-intercept form: y = mx + b

(m is the slope, b is the y-intercept or the y value when x = 0 --> (0, y) or the point where the line crosses through the y-axis)

For lines to be perpendicular, their slopes have to be the negative reciprocal of each other. (Basically flip the sign +/- and the fraction[switch the numerator and the denominator])

For example:

Slope =
(1)/(3)

Perpendicular line's slope =
-(3)/(1) or -3

Slope = -2 or
-(2)/(1)

Perpendicular line's slope =
(1)/(2)


y=(1)/(3) x+5 The given line's slope is
(1)/(3), so the perpendicular line's slope is -3. Now that you know the slope, substitute/plug it into the equation:

y = mx + b

y = -3x + b To find b, plug in the point (1, 9) and isolate/get the variable "b" by itself in the equation

9 = -3(1) + b Add 3 on both sides to get "b" by itself

9 + 3 = -3 + 3 + b

12 = b

y = -3x + 12

User Tridus
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