LilVeroDez13
Suppose B is the midpoint of AC. AB = 5x and BC = 3x + 4. Find AB. (Hint: Make a sketch and write an equation to solve.)
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jim_thompson5910
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B is the midpoint, so AB and BC are equal pieces that make up AC
jim_thompson5910
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this means
AB = BC
5x = 3x+4
LilVeroDez13
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So then i would solve for x?
jim_thompson5910
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yes you would
jim_thompson5910
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tell me what you get
LilVeroDez13
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I get .5.. but i know thats wrong.. so, 5x = 3x + 4.. u combine like terms.. right?
jim_thompson5910
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subtract 3x from both sides
jim_thompson5910
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5x = 3x + 4
5x-3x = 3x + 4-3x
2x = 4
jim_thompson5910
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whats next?
LilVeroDez13
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divide 2 do both sides.. x = 2
jim_thompson5910
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exactly, now use this to find AB
LilVeroDez13
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5(2) = 10 :)
jim_thompson5910
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you nailed it
LilVeroDez13
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Thanks!! :) Can u help me with another question
LilVeroDez13
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Thanks!! :))
Four points A, B, C, and D are coplanar, but only two at a time are collinear. Suppose a line is drawn through each pair of points. How many lines can you draw?
jim_thompson5910
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Four points A, B, C, and D are coplanar means that all four points lie in the same plane
jim_thompson5910
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but only two at a time are collinear
means that all 4 points do NOT form a straight line
also, it means that there are no 3 points that form a straight line
jim_thompson5910
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so we might have something like this
|dw:1348964739339:dw|
jim_thompson5910
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Here are two pairs of lines
|dw:1348964798916:dw|
jim_thompson5910
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oops just meant to say "here are a pair of lines"
jim_thompson5910
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Here's another pair
|dw:1348964855161:dw|
jim_thompson5910
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and another pair
|dw:1348964897439:dw|
jim_thompson5910
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and that's all we can draw because there are no other possible pairs of lines to draw
LilVeroDez13
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:) So, there are 4 possible ways?
jim_thompson5910
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double that to get 8
jim_thompson5910
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4 pairs of lines = 8 lines
LilVeroDez13
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Ahh.. i see now. Thanks so much!! ur really smart :) geometry kicks my butt. You make it easy to understand :)
jim_thompson5910
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oh wait, i'm counting 3 pairs (not sure where I got 4 pairs)
so 3 pairs = 6 lines
jim_thompson5910
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I'm glad I do