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# The points A, B and C lie on the straight line y= 2x-1

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The points A, B and C lie on the straight line y= 2x-1

The coordinates of a are (2, 3)

The coordinates of B are (5, 9)

Given that AC = 3AB, find the coordinates of C

YEEEEEET  Mar 25, 2018
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#1
+85759
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C  =  [  2 + ( 5 -2)*3  ,  3 + (9 - 3)*3 ]  =  [ 2 + 9, 3 + 18 ]  =  ( 11, 21 )

CPhill  Mar 25, 2018
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can you explain why please, thanks

YEEEEEET  Mar 25, 2018
#3
+85759
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OK

We need to  find the difference between the x coordinates of A and B= (5 -2)  =3

Since  AC  = 3AB

3 times this difference plus the x  coordinate of A  will give us the x coordinate of C

So    3(5-2)  + 2  =   3*3  + 2  = 11

Similarly.......3 times the difference between the y coordinates of A  and B  plus the y coordinate of A  will give us the y coordinate of C....so we have

3 ( 9 - 3)  +  3   =  3*6  + 3  =  21

So....the coordinates of C   are   (11, 21)

CPhill  Mar 25, 2018

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