Question 187095
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Remember that your points are expressed as ordered pairs (<i>x</i>,<i>y</i>).


Step 1:  Subtract the second <i>y</i> value from the first <i>y</i> value:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 6 - 8 = -2]


Step 2:  Subtract the second <i>x</i> value from the first <i>x</i> value:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -10 - (-5) = -5]


Step 3:  Divide the results of Step 1 by the results of Step 2:



*[tex \LARGE \ \ \ \ \ \ \ \ \ \ m_{AB}\ =\ \frac{-2}{-5}\ =\ \frac{2}{5}]


In general, given *[tex \Large P_1(x_1,y_1)] and *[tex \Large P_2(x_2,y_2)] the slope *[tex \Large m_1] of line *[tex \Large L_1] through *[tex \Large P_1] and *[tex \Large P_2] is given by:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ m_1\ =\ \frac{y_1 - y_2}{x_1 - x_2} ]


Note that it doesn't matter which of the two points you say is the 'first' and which the 'second' because, specifically for your problem:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ m_{BA}\ =\ \frac{8 - 6}{-5 - (-10)}\ =\ \frac{2}{5} ]


And in general:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ m_1\ =\ \frac{y_1 - y_2}{x_1 - x_2}\ =\ \frac{-(y_2 - y_1)}{-(x_2 - x_1)}\ =\ \frac{y_2 - y_1}{x_2 - x_1}]


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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