Analytic Geometry Q6

**looi76** · January 31st 2009, 02:13 AM

Question:
Using slopes, determine if the points lie on a straight line.
a) $(-1,-4)$ , $(3,8)$ & $(0,-1)$
b) $(0,5)$ , $(-1,3)$ & $(-3,2)$

Attempt:

a) $(-1,-4)$ & $(3,8)$

$m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{8-(-4)}{3-(-1)} = \frac{12}{4} = 3$

$(3,8)$ & $(0,-1)$

$m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{-1-8}{0-3} = \frac{-9}{-3} = 3$

It is a straight line as the slopes are the same.

b) $(0,5)$ & $(-1,3)$

$m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{3-5}{-1-0} = 2$

$(-3,2)$ & $(-1,3)$

$m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{3-2}{(-1)-3} = \frac{1}{-4} = -\frac{1}{4}$

It is not a straight line as the slopes don't match.

are my answers correct?

**running-gag** · January 31st 2009, 02:27 AM

a) you data is (0,1) but you made the calculation with (0,-1)

b) your calculation of the second slope is not correct

**looi76** · January 31st 2009, 02:35 AM

a) I have corrected the question. Is my answer right?

b) $(-3,2)$ & $(-1,3)$

$\color{red}{m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{3-2}{(-1)-3} = \frac{1}{-4} = -\frac{1}{4}}$

$m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{2-3}{-3-1} = \frac{1}{4}$

It is still not a straight line, am I right?

**running-gag** · January 31st 2009, 04:14 AM

a) OK

b) The slope is still not correct ...

Thread: Analytic Geometry Q6

LinkBack

Thread Tools

Display

Analytic Geometry Q6

Similar Math Help Forum Discussions

Analytic Geometry Q7

Analytic Geometry Q5

Analytic Geometry Q2

Analytic Geometry Help!

help on analytic geometry

Search Tags