Question of Form 4 - Chapter 6 Coordinate Geometry

[[Announcements] [Introduce Yourself] [ICT] [Prasekolah] [LINUS] [KSSR] [UPSR] [PMR] [SPM] [STPM] [School] [Classroom] [Clubs & Uniformed Bodies] [JPN] [SPA] [SICT] [SPP] [SPS] [SPPK] [SPSPK] [SPI] [SPsK] [JNJK] [PPD] [Program] [Computer & Internet] [Let's Hear It From You] [Membergroup]]

[Announcements] [Introduce Yourself] [ICT] [Prasekolah] [LINUS] [KSSR] [UPSR] [PMR] [SPM] [STPM] [School] [Classroom] [Clubs & Uniformed Bodies] [JPN] [SPA] [SICT] [SPP] [SPS] [SPPK] [SPSPK] [SPI] [SPsK] [JNJK] [PPD] [Program] [Computer & Internet] [Let's Hear It From You] [Membergroup]

[Jenna Tan]

The point A( 2a, a) , B( b ,c ) and C( 2b, 3c) are on a straight line . B divides AC internally in the ratio 3:4.
Express b in term c .

answer is : b=-4c

I only know that the formula for this question is

The point which divides the line joining two points
(x_{1}, y_{1}), (x_{2}, y_{2})
in the ratio m:n internally is
(\frac{mx_{2}+nx_{1}}{m+n}, \frac{my_{2}+ny_{1}}{m+n}).

Is that correct?

I have tried to solve the question using the formula above, but I did halfway only.
Because I don't know how to proceed by expressing b in term c.

[Siao Fong Ting]

comparing the x-coordinate for point B and the x-coordinate obtained using the formula,  (6b+8a)/7 = b
             6b + 8a = 7b
             b = 8a -- (1)



comparing the y-coordinate for point B and the y-coordinate obtained using the formula, (9c+4a)/7 = c
            9c + 4a = 7c
                   4a = -2c
                    a = - (1/2)c  --(2)

substitude (2) to (1)
             b = 8 (-1/2)c
                = -4c

[Jenna Tan]

comparing the x-coordinate for point B and the x-coordinate obtained using the formula,  (6b+8a)/7 = b
             6b + 8a = 7b
             b = 8a -- (1)



comparing the y-coordinate for point B and the y-coordinate obtained using the formula, (9c+4a)/7 = c
            9c + 4a = 7c
                   4a = -2c
                    a = - (1/2)c  --(2)

substitude (2) to (1)
             b = 8 (-1/2)c
                = -4c

Oh I see...
I did wrong from the beginning ! 
Now I understand .
Thanks for your help ! 

Advanced search