Finding the gradient of a line - please help! Watch

Emily Josephine
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I understand the basics of finding the gradient of a line but am getting confused with this particlar question. If you can explain how to get to the answer, that'd be great. Question: Find the gradient of the line joining the pair of points with coordinates (p+3,p-3),(2p+4,-p-5) Answer: -2 I've been using the equation of Y2-Y1/X2-X1
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ghostwalker
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(Original post by Emily Josephine)
I understand the basics of finding the gradient of a line but am getting confused with this particlar question. If you can explain how to get to the answer, that'd be great. Question: Find the gradient of the line joining the pair of points with coordinates (p+3,p-3),(2p+4,-p-5) Answer: -2 I've been using the equation of Y2-Y1/X2-X1
It's just a question of plugging in the values, and then simplifying.

If you've done it correctly, you can factor out "p+1" in your working.

If not, post your working so far.
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Emily Josephine
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Here is my working:

Y2 - Y1 = (-p-5)-(p-3) = -p-5-p-3 = -2p-8
X2 - X1 = (2p+4)-(p+3) = 2p+4-p+3 = p+7

so then...

-2p-8 / p+7 = ????

I'm lost and can't see how it equals -2
I know I must have gone wrong, just can't get my head around it
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old_engineer
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Couple of things:
-5 - (-3) = -5 + 3 = -2
4 - (+3) = 4 - 3 = 1
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Emily Josephine
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Thank you! That makes sense! I just expanded the brackets wrong. Just to check this is now my workings:
-2p-2/1p+1 = -2-2/2 = -4/2 = -2

I hope that's right... But feel I've over complicated it. Is there a simpler way?
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mqb2766
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(Original post by Emily Josephine)
Thank you! That makes sense! I just expanded the brackets wrong. Just to check this is now my workings:
-2p-2/1p+1 = -2-2/2 = -4/2 = -2

I hope that's right... But feel I've over complicated it. Is there a simpler way?
The p can't just disappear
-2p - 2 = -2(p+1)
1p+1 = (p+1)
The (p+1) factor cancels in both top and bottom.
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old_engineer
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(Original post by Emily Josephine)
Thank you! That makes sense! I just expanded the brackets wrong. Just to check this is now my workings:
-2p-2/1p+1 = -2-2/2 = -4/2 = -2

I hope that's right... But feel I've over complicated it. Is there a simpler way?
No that’s not right, as you seem to have set p = 1 with no justification.
(-2p - 2)/(p + 1) = -2(p + 1)/(p + 1) then cancel (p + 1) from top and bottom.
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Emily Josephine
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Oh right I see. Thank you so much for your help!
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