Asked by Hannah

1. A, B and C are collinear, and B is between A and C. The ratio of AB to AC is 3:4. If A is at (-8,1) and B is at (-2,-2), what are the coordinates of C?

2. The segment joining (1,-3) and (4,-6) is extended a distance equal to one-sixth of its own length. Find the terminal point.

I solved these two problems yet neither of them is correct.

Answers

Answered by oobleck
AB:AC = 3:4 means that B is 3/4 of the way from A to C.
Think about it. Start at A. When you get to B, AB is 3/4 of the whole distance AC.
B = A + k (C-A)
when k=0, you are at A
when k=1, you are at C
Bx = Ax + 3/4 (Cx - Ax) = -8 + 3/4 (-2+8) = -8 + 3/4 (6) = -7/2
That is, the distance from -8 to -2 is 6. 3/4 of 6 = 9/2
By = 1 + 3/4 (-2-1) = 1 + 3/4 (-3) = -5/4

For #2, If we let A = (1,-3) and B = (4,-6), we want C such that BC = 1/6 AB
That is, AC:AB = 7/6
Cx = Ax + 7/6 (Bx - Ax) = 1 + 7/6 (4-1) = 9/2
Cy = -3 + 7/6 (-6+3) = -3 + 7/6 (-3) = -13/2
So, C = (9/2, -13/2)

You really should get out some graph paper and plot the points, to make sure your answer satisfies the conditions. It may be easier to see geometrically.
Answered by Kristine Morales
(0,-3)
Answered by Joanna
I checked, its (0, -3)

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