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## #1 Re: Help Me ! » Stuck on a difficult co-ordinate geomatry problem » 2005-11-21 05:19:45

At (-2,4):   4 = m(-2) + c → c = 4+2m
At (x1,0):  0 = m(x1) + c→ x1 = -c/m
At (0,y1)   y1 = m(0) + c  → y1 = c

x1+y1 = -4
∴-c/m +c=-4/1
y1=c
c=2m+4

next substitute c value for c into equation: -c/m +c=-4/1

(-2m+4)/m +2m+4=-4

2m+4+2m²+4m=0
since 2m+4=c==y1
then x1+4= 2m²+4m

I still can't get it out any ideas anyone. I guess I went hopelessly wrong

## #2 Re: Help Me ! » Stuck on a difficult co-ordinate geomatry problem » 2005-11-20 09:48:05

Sorry I see what was wrong I made a mistake when typing the question. I should have been x1 + y1=-4 not x1 + y1=-4m . Thanks for all your help though. Can your method still work with this equation?

## #3 Re: Help Me ! » Stuck on a difficult co-ordinate geomatry problem » 2005-11-20 09:45:08

Something seems worng as I checked the answer at the back of the book and the answers for m were supposed to be either -1 or 2

## #4 Introductions » Hello » 2005-11-20 07:50:07

Sephiroth Valentine
Replies: 2

Hi, my names Jonathan.I'm studing higher level maths for the leaving Cert in Ireland. I'm finding it really difficult, so i'll apologise in advance for asking too many questions.Nice to meet you all.

## #5 Help Me ! » Stuck on a difficult co-ordinate geomatry problem » 2005-11-20 07:45:58

Sephiroth Valentine
Replies: 6

6(C) A line containg the point(-2,4) has a slope of m which is not equal to zero. The line intercepts the x-axis at (x1,0) and the y axis at (0,y1) If x1 + y1=-4m find the slopes of the two lines that satisfy this condition. Hence find the tangent of the acute angle between these two lines.

I really don't know where to start Tried using the slope formula y2-y1/x2-x1 using the point (-2,4) and (x1,0) and then I used the points (-2,4) and (0,y1) to get another value for m. I put bothe equal to one another but I could'nt get a value to work out. Could any help me please.

## #6 Help Me ! » Can any one help me with a coordinate geometry problem » 2005-11-19 11:06:48

Sephiroth Valentine
Replies: 2

rstu is a quadrilateral where r = (-1,-5) and s =  (13,9)
q(3,-1) lies on the line rs.

(i) The coordinates of u are (-2k,3k)
where k∈R and k>0

The area of the triangle rqu is 28 square units. Find the value of k.

(II) The slope of ts is -3/11 and sr are parallel to tu. Find the coordinates of t.

Would anyone be able to tell me the steps to take to solve these questions or would be able to offer suggestions of how to solve them thanks. Much appreciated