December 1st, 2014, 04:34 PM  #1 
Newbie Joined: Oct 2014 From: usa Posts: 10 Thanks: 0  Coordinate Geometry!!
Please friends help me out with this probem..!! Que) In the x,y coordinate system, line l passes through point P(2, 1) and is perpendicular to line y = x + 1. Column A y intercept of line l Column B x intercept of line l Ans) (a) The quantity in Column A is greater. (b) The quantity in Column B is greater. (c) The two quantities are equal. (d) The relationship cannot be determined from the information given. Please explain stepwise, as I am weak in coordinate geometry. Last edited by skipjack; December 1st, 2014 at 08:10 PM. 
December 1st, 2014, 07:45 PM  #2 
Senior Member Joined: Jan 2012 From: Erewhon Posts: 245 Thanks: 112 
That a line is perpendicular to $y=x+1$ means that its slope is $1$. So we may write the equation of the line as $y=x+c$. We are told the line passes through the point $P(2,1)$, so we have when $x=2$ that $y=1$, so: $1=2+c$ so $c=3$ and our line is $y=x+3$ ... Now complete the answer yourself. CB Last edited by skipjack; December 1st, 2014 at 08:06 PM. 
December 1st, 2014, 08:18 PM  #3 
Global Moderator Joined: Dec 2006 Posts: 20,629 Thanks: 2077 
One needn't find the value of c.

December 2nd, 2014, 04:43 AM  #4 
Senior Member Joined: Jan 2012 From: Erewhon Posts: 245 Thanks: 112  You don't need to even find the slope the solution can be found perfectly well by construction with straight edge and compass. So other than your snarky comment what help to solve this, without finding c, are you offering the OP? CB Last edited by greg1313; December 2nd, 2014 at 08:10 PM. 
December 2nd, 2014, 05:32 PM  #5 
Global Moderator Joined: Dec 2006 Posts: 20,629 Thanks: 2077 
In this instance, it's quite likely that any working is ignored, as the question is of the multiple choice type. In general, though, it's better to explain the key points, i.e., explain why the gradient is 1, etc., than to write considerably more to obtain something that isn't necessary and so wouldn't be awarded any marks.

December 2nd, 2014, 08:24 PM  #6  
Senior Member Joined: Jan 2012 From: Erewhon Posts: 245 Thanks: 112  Quote:
CB  
December 3rd, 2014, 07:55 AM  #7 
Global Moderator Joined: Dec 2006 Posts: 20,629 Thanks: 2077 
The question doesn't request that. It presents four answers, so selecting the appropriate answer suffices. At the start of a multiple choice paper, there is an instruction to select the appropriate answer from the choices given for each question.

December 3rd, 2014, 11:20 AM  #8 
Newbie Joined: Oct 2014 From: usa Posts: 10 Thanks: 0 
Hello Friends..!! Thank you so much for your replies...If we don't find the value of c then, please explain the other method to solve it. Last edited by skipjack; December 3rd, 2014 at 02:35 PM. 
December 3rd, 2014, 02:37 PM  #9 
Global Moderator Joined: Dec 2006 Posts: 20,629 Thanks: 2077 
The intercepts can be given very simply in terms of c. However, what would you consider to be the definitions of "x intercept" and "y intercept"? Should an intercept be referred to as a quantity?

December 3rd, 2014, 11:39 PM  #10  
Senior Member Joined: Jan 2012 From: Erewhon Posts: 245 Thanks: 112  Quote:
As a global moderator I expect you in addition to keeping order on the site to at least attempt to help those innocently seeking help and as far as I can see you are not. If I was uncharitable (and I'm not) I would describe your contribution as a waste of space. CB Last edited by skipjack; December 4th, 2014 at 02:17 AM.  

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