SOLUTION: What is the equation of the line in slope-intercept form? the line perpendicular to y = 1/3x+5 through (2, 1) A) y = 1/3x+7 B) y = -3+7 C) y = 3x+7 D) Y = -1/3x+7

Question 668886: What is the equation of the line in slope-intercept form? the line perpendicular to y = 1/3x+5 through (2, 1)
A) y = 1/3x+7
B) y = -3+7
C) y = 3x+7
D) Y = -1/3x+7
Found 2 solutions by MathLover1, ewatrrr:
Answer by MathLover1(20849) (Show Source): You can put this solution on YOUR website!

Solved by pluggable solver: Finding the Equation of a Line Parallel or Perpendicular to a Given Line

Remember, any two perpendicular lines are negative reciprocals of each other. So if you're given the slope of , you can find the perpendicular slope by this formula:

where is the perpendicular slope

So plug in the given slope to find the perpendicular slope

When you divide fractions, you multiply the first fraction (which is really ) by the reciprocal of the second

Multiply the fractions.

So the perpendicular slope is

So now we know the slope of the unknown line is (its the negative reciprocal of from the line ). Also since the unknown line goes through (2,1), we can find the equation by plugging in this info into the point-slope formula

Point-Slope Formula:

where m is the slope and (,) is the given point

Plug in , , and

Distribute

Multiply

Add to both sides to isolate y

Combine like terms

So the equation of the line that is perpendicular to and goes through (,) is

So here are the graphs of the equations and

graph of the given equation (red) and graph of the line (green) that is perpendicular to the given graph and goes through (,)

so, the answer is:
B) ........you are missing variable here, should be B)
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!

Hi,
line perpendicular to y = 1/3x+5 through (2, 1)
m = -3
y= -3x + b
1 = -3*2 + b ||Using (x,y)ordered pair(2,1) to solve for b
7 = b
y = -3x + 7
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