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Foot of perpendicular

  • Thread starter MMCS
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  • #1
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I apologise in advance for an extremely trivial question, i am returning to brush up on some basic maths and cant seem to arrive at the answer

Find the coordinates of the foot of the perpendicular from the point A with coordinates (-5,5) to the line 10x+2y-3= 0

1.) gradient of original line -10/2, gradient of intercepting line 1/5
2.) equation of intercepting line y-5 = 1/5(x+1) *5
3.)5y-25 = x+1 re-arranging gives 5y-x = 26
4.) solve simultaneously -10x-50y=-260 ( *-10 )
10x+2y=3

-48y=-257

y=5.354
Substituting y into either equation
x= -0.7708

From the program i know these answers arnt correct

Any pointers would be appreciated,

Thanks
 

Answers and Replies

  • #2
33,098
4,797
I apologise in advance for an extremely trivial question, i am returning to brush up on some basic maths and cant seem to arrive at the answer

Find the coordinates of the foot of the perpendicular from the point A with coordinates (-5,5) to the line 10x+2y-3= 0

1.) gradient of original line -10/2, gradient of intercepting line 1/5
2.) equation of intercepting line y-5 = 1/5(x+1) *5
Mistake above. The known point on the intersecting line is (-5, 5), so the equation of this line would be y - 5 = (1/5)(x - (-5))

Why do you have "*5" on the right side of your equation?
3.)5y-25 = x+1 re-arranging gives 5y-x = 26
4.) solve simultaneously -10x-50y=-260 ( *-10 )
10x+2y=3

-48y=-257

y=5.354
Substituting y into either equation
x= -0.7708

From the program i know these answers arnt correct

Any pointers would be appreciated,

Thanks
 
  • #3
151
0
Hi,

I had the *5 to remove the fraction, dont know how i ended up with the 1 on the right hand side. That sorted it. Thanks for spotting that, such a silly mistake. Wouldnt think id been staring at it for half an hour. Probably suggests i need some sleep :bugeye:
 
  • #4
ehild
Homework Helper
15,396
1,803
I apologise in advance for an extremely trivial question, i am returning to brush up on some basic maths and cant seem to arrive at the answer

Find the coordinates of the foot of the perpendicular from the point A with coordinates (-5,5) to the line 10x+2y-3= 0

1.) gradient of original line -10/2, gradient of intercepting line 1/5
2.) equation of intercepting line y-5 = 1/5(x+1) *5
Check the red part.

ehild
 
  • #5
33,098
4,797
Hi,

I had the *5 to remove the fraction
If you multiply one side by 5, you need to also multiply the other side by the same number. Maybe you did this, but it doesn't show in your work.

It's best to start a new line when you do this kind of operation.
, dont know how i ended up with the 1 on the right hand side. That sorted it. Thanks for spotting that, such a silly mistake. Wouldnt think id been staring at it for half an hour. Probably suggests i need some sleep :bugeye:
 

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