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avatar+25 

Hi there everyone!  I'm stuck on question 2c (find the exact x coordinate of E).  Please help, thanks. 

 Oct 21, 2019
 #1
avatar+104911 
+1

First, find the slope of  AD   = [ 7 - 2 ]           5             5

                                              _______  =   -----  =    - ___

                                                 [ 1 - 8]          -7             7

 

The slope of  a perpendicular line to this  =  7

                                                                    __

                                                                      5

 

So....using D  and  this slope we have that

 

y = (7/5) ( x - 8)  + 2         multiply through by  5

 

5y  = 7 (x - 8) + 10

 

5y =  7x  -  56  +  10

 

5y =  7x   - 46

 

-7x + 5y  =  -46     multiply  through by   -1

 

7x   -   5y   =   46      (1)

 

This line will intersect AB

 

The equation of  AB  is  y   = 7

 

Sub   y = 7   into (1)   and we have that

 

7x  - 5(7)   = 46

 

7x  -  35  =  46       add   35 to both sides

 

7x  =  81        divide both sides by  7

 

x  =  81/7 =  x coordinate of E

 

So    

 

E  = (81/7, 7)

 

 

cool cool cool

 Oct 21, 2019
 #2
avatar+25 
+1

Thank you so much!  It was finding the equation of AB that got me confused on this question.   Much appreciated. 

Umbrella  Oct 21, 2019
 #3
avatar+104911 
+1

OK....you're welcome   !!!

 

cool cool cool

CPhill  Oct 21, 2019

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