I know the formula for this type of problem is the second y coordinate subtracted from the first y coordinate over the second x coordinate subtracted from the first x coordinate but for the numbers given to me for this problem (-9, - 5) and (-7, 5) it says the slope = 5 I am getting 10 over 16. Am I doing something wrong?
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It is 10 over 2. – Fermat Apr 27 '15 at 19:55
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Yes: $-7-(-9)=2$. – Vincenzo Tibullo Apr 27 '15 at 19:55
2 Answers
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The problem is you aren't subtracting in the denominator.
As you said, the slope of the line passing through $(x_{1},y_{1})$ and $(x_{2},y_{2})$ is $\dfrac{y_{2} - y_{1}}{x_{2} - x_{1}}$.
You have the points $(-9, -5)$ and $(-7,5)$.
You have been calculating this as $\dfrac{-5 - 5}{-9 + -7} = \dfrac{-10}{-16}$. Notice that you did $x_{2} + x_{1}$ in the denominator, not $x_{2} - x_{1}$.
The correct answer is $\dfrac{-5 - 5}{-9 - (-7)} = \dfrac{-10}{-9 + 7} = \dfrac{-10}{-2} = 5$.
layman
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