err., i missed one of my additional math class and I don't kno how to solve this Q:
-show that (-1,-5), (2,1), (4,5), and (6,9) lie on a straight line.
thanks for ur help!!!
*no harsh word please...
2007-07-05 00:32:18 · 4 answers · asked by kit 3 in Education & Reference ➔ Homework Help
hi
you need just to find the slope of the line which fits all these point.
and in the same idea,,,u can write the Equation of the line by finding the slope between any two points of them..and you will got the slope which is 2.
regards
2007-07-05 00:38:55 · answer #1 · answered by ahmed_mhanna 1 · 1⤊ 0⤋
I don't think any of the solutions posted so far are completely
right. Remember that parallel lines have the same
slope, so the last 2 points might lie on a line parallel
to the line joining the first 2. Let's find the equation
of the line joining the first two points.
The slope of that line is
( 1 -(-5) )/ (2 - (-1) ) = 6/3 = 2.
So
y = 2x + b
Now plug in either point, say (2,1)
1 = 4 + b
b = -3
So the equation is
y = 2x -3
Now let's see if the other 2 points satisfy this equation:
(4,5):
5 = 2*4-3 OK.
(6,9)
9 = 2*6 -3 OK.
So all the points do lie on the line
y = 2x-3.
2007-07-05 10:15:03 · answer #2 · answered by steiner1745 7 · 1⤊ 0⤋
Sorry, no genius. Nor required. ahmed is right.
For this question take (-1,-5) as reference. For each of the other points find the ratio of the difference in Y co-ordinates with the reference point and that between the X co-ordinates with the reference point.
they are 1-(-5)/(2-(-1))=6/3=2
5-(-5)/(4-(-1))=10/5=2
9-(-5)/(6-(-1))=14/7=2
This shows that all three pairs have the same slope, so all lie on one line.
2007-07-05 10:00:17 · answer #3 · answered by A.V.R. 7 · 1⤊ 0⤋
Draw a graph, yhen mark the releveant points on the graph and join the dots. If that makes a straight line you have proved the question.
2007-07-05 07:41:34 · answer #4 · answered by bri 7 · 1⤊ 2⤋