My Math Forum The Equation of Line

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September 15th, 2013, 04:32 AM   #1
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The Equation of Line

My final answer matches that of the text book, but can anyone confirm if the 1st part of my answer is sufficient or do I need to prove L = 1 mathematically? Many thanks.

Q. The line L cuts equal intercepts from the x-axis & y-axis as shown (see attachment). Find the equation of L if (-1, 3) $\in$ L.

Attempt: Because the intercepts are equal, the slope of L = 1.
Thus, $y-3=1(x-(-1))\rightarrow y-3=x+1\rightarrow x-y+4=0$
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 September 15th, 2013, 07:22 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,969 Thanks: 2217 The question's wording is poor. The intercepts shown are equal in magnitude, but not in sign. If they were equal in magnitude and sign, the slope of the line would be -1. Strictly speaking, therefore, your answer should have started "Because the intercepts are equal in magnitude and opposite in sign" (or equivalent wording).
 September 15th, 2013, 10:04 AM #3 Senior Member   Joined: Sep 2011 Posts: 395 Thanks: 0 Re: The Equation of Line Ok, thank you.

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