SOLUTION: Tutor, I just want to make sure that I have solved this question correctly. Write the equation of the line L satisfying the given geometric conditions. 40. L has y-in

Algebra ->  Linear-equations -> SOLUTION: Tutor, I just want to make sure that I have solved this question correctly. Write the equation of the line L satisfying the given geometric conditions. 40. L has y-in      Log On


   

Question 90537This question is from textbook Beginning Algebra
: Tutor,
I just want to make sure that I have solved this question correctly.
Write the equation of the line L satisfying the given geometric conditions.
40. L has y-intercept (0,2) and is perpendicular to the line with equation
2x - 3y = 6.
I got y = -1/2x - 4 is this correct?
Thanks in advance for your assistance. This question is from textbook Beginning Algebra

Found 2 solutions by kev82, jim_thompson5910:
Answer by kev82(151) About Me  (Show Source):
You can put this solution on YOUR website!
Hi,

Sorry, I'm afraid you haven't got it right. Firstly, the y intercept (this is when x=0) should be 2. and if I put x=2 into your answer I get -4. But also your answer isn't perpendicular.

I don't want to do this by a method you haven't seen, because that will most likely be very confusing. How have you been taught to find a line perpensicular to a given one?

Kev

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
First convert 2x - 3y = 6 to slope intercept form

Solved by pluggable solver: Converting Linear Equations in Standard form to Slope-Intercept Form (and vice versa)
Convert from standard form (Ax+By = C) to slope-intercept form (y = mx+b)


2x-3y=6 Start with the given equation


2x-3y-2x=6-2x Subtract 2x from both sides


-3y=-2x%2B6 Simplify


%28-3y%29%2F%28-3%29=%28-2x%2B6%29%2F%28-3%29 Divide both sides by -3 to isolate y


y+=+%28-2x%29%2F%28-3%29%2B%286%29%2F%28-3%29 Break up the fraction on the right hand side


y+=+%282%2F3%29x-2 Reduce and simplify


The original equation 2x-3y=6 (standard form) is equivalent to y+=+%282%2F3%29x-2 (slope-intercept form)


The equation y+=+%282%2F3%29x-2 is in the form y=mx%2Bb where m=2%2F3 is the slope and b=-2 is the y intercept.






Now lets find the line perpendicular to y=%282%2F3%29x-2 going through (0,2)

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 2%2F3, you can find the perpendicular slope by this formula:

m%5Bp%5D=-1%2Fm where m%5Bp%5D is the perpendicular slope


m%5Bp%5D=-1%2F%282%2F3%29 So plug in the given slope to find the perpendicular slope



m%5Bp%5D=%28-1%2F1%29%283%2F2%29 When you divide fractions, you multiply the first fraction (which is really 1%2F1) by the reciprocal of the second



m%5Bp%5D=-3%2F2 Multiply the fractions.


So the perpendicular slope is -3%2F2



So now we know the slope of the unknown line is -3%2F2 (its the negative reciprocal of 2%2F3 from the line y=%282%2F3%29%2Ax-2). Also since the unknown line goes through (0,2), we can find the equation by plugging in this info into the point-slope formula

Point-Slope Formula:

y-y%5B1%5D=m%28x-x%5B1%5D%29 where m is the slope and (x%5B1%5D,y%5B1%5D) is the given point



y-2=%28-3%2F2%29%2A%28x-0%29 Plug in m=-3%2F2, x%5B1%5D=0, and y%5B1%5D=2



y-2=%28-3%2F2%29%2Ax%2B%283%2F2%29%280%29 Distribute -3%2F2



y-2=%28-3%2F2%29%2Ax-0%2F2 Multiply



y=%28-3%2F2%29%2Ax-0%2F2%2B2Add 2 to both sides to isolate y

y=%28-3%2F2%29%2Ax-0%2F2%2B4%2F2 Make into equivalent fractions with equal denominators



y=%28-3%2F2%29%2Ax%2B4%2F2 Combine the fractions



y=%28-3%2F2%29%2Ax%2B2 Reduce any fractions

So the equation of the line that is perpendicular to y=%282%2F3%29%2Ax-2 and goes through (0,2) is y=%28-3%2F2%29%2Ax%2B2


So here are the graphs of the equations y=%282%2F3%29%2Ax-2 and y=%28-3%2F2%29%2Ax%2B2




graph of the given equation y=%282%2F3%29%2Ax-2 (red) and graph of the line y=%28-3%2F2%29%2Ax%2B2(green) that is perpendicular to the given graph and goes through (0,2)