0
$\begingroup$

I'm using this formula to work out the equation of a line joining points $(1,5)$ and $(-9,2)$:

$ \frac{y-y_1}{y_2-y_1} = \frac{x-x_1}{x_2-x_1}$

Like this:

$ \frac{y-5}{2-5} = \frac{x-1}{-9-1}$

$= \frac{y-5}{-3} = \frac{x-1}{10}$

$= y-5= -3\frac{x-1}{10}$

$= y-5= \frac{-3x-(-3)}{10}$

$= y= \frac{-3x + 3}{10} + 5$

$= y= \frac{-3x + 53}{10}$

$Answer: y= \frac{-3}{10}x + \frac{53}{10}$

My book gives the answer as:

$ y= \frac{3}{10}x + \frac{47}{10}$

I can't see what I'm doing wrong. Any help greatly appreciated.

  • 0
    the gentleman is right but before asking try to solve it once more using a fresh sheet of paper and without referring to the last solution...really takes you along way :)2012-04-06

1 Answers 1

3

In the third line, you move from -9-1 to 10. That should be a -10. Hope this helps!

  • 0
    Thank you very much! What a silly mistake!2012-04-06