SOLUTION: Find equation for a line Express answer using slope intercept perpendicular to the line y=2x-5 points (-1,-2) how do I do this problem?

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Question 101506: Find equation for a line Express answer using slope intercept perpendicular to the line y=2x-5 points (-1,-2) how do I do this problem?
Answer by jim_thompson5910(35256) About Me  (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 2, 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%2F1%29 So plug in the given slope to find the perpendicular slope



m%5Bp%5D=%28-1%2F1%29%281%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=-1%2F2 Multiply the fractions.


So the perpendicular slope is -1%2F2



So now we know the slope of the unknown line is -1%2F2 (its the negative reciprocal of 2 from the line y=2%2Ax-5). Also since the unknown line goes through (-1,-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%2B2=%28-1%2F2%29%2A%28x%2B1%29 Plug in m=-1%2F2, x%5B1%5D=-1, and y%5B1%5D=-2



y%2B2=%28-1%2F2%29%2Ax%2B%281%2F2%29%28-1%29 Distribute -1%2F2



y%2B2=%28-1%2F2%29%2Ax-1%2F2 Multiply



y=%28-1%2F2%29%2Ax-1%2F2-2Subtract -2 from both sides to isolate y

y=%28-1%2F2%29%2Ax-1%2F2-4%2F2 Make into equivalent fractions with equal denominators



y=%28-1%2F2%29%2Ax-5%2F2 Combine the fractions



y=%28-1%2F2%29%2Ax-5%2F2 Reduce any fractions

So the equation of the line that is perpendicular to y=2%2Ax-5 and goes through (-1,-2) is y=%28-1%2F2%29%2Ax-5%2F2


So here are the graphs of the equations y=2%2Ax-5 and y=%28-1%2F2%29%2Ax-5%2F2




graph of the given equation y=2%2Ax-5 (red) and graph of the line y=%28-1%2F2%29%2Ax-5%2F2(green) that is perpendicular to the given graph and goes through (-1,-2)