dlxpxv7的部落格

標題:

Find the coordinates?

發問:

If the coordinates of A is (-7 ,-12) and C is (5,3) . B is a point on the x-axis such that the slope of AB is triple that of BC . Find the coordinates of B.

最佳解答:

• geometry 03' #17
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Let (k,0) be the coordinates of B. slope of AB=(-12-0)/(-7-k)=-12/(-7-k)=12/(7+k) slope of BC=(0-3)/(k-5)=-3/(k-5)=3/(5-k) 12/(7+k)=3*3/(5-k) 12/(7+k)=9/(5-k) 12(5-k)=9(7+k) 60-12k=63+9k -3=21k k=-1/7 coordinates of B=(-1/7,0)

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