# Writing the equation of the line...

• February 22nd 2010, 09:56 AM
PiratePrincess
Writing the equation of the line...
Hi there can you help me find the equation of the line that has a slope of -4/3 and passes through (-2,5) ?

Thank you!
• February 22nd 2010, 10:12 AM
mathemagister
Quote:

Originally Posted by PiratePrincess
Hi there can you help me find the equation of the line that has a slope of -4/3 and passes through (-2,5) ?

Thank you!

The formula for the equation of a line knowing 2 points and a slope is:

$y-y_1 = m(x-x_1)$ where m is the slope and $x1$ and $y1$ are the coordinates of the given point.

Simply substitute:

$y-5 = -\frac{4}{3} (x- (-2))$ and clean up if you want. Usually, on AP Calc tests, they recommend you don't waste your time simplifying because they accept this answer.
• February 22nd 2010, 03:04 PM
integral
$y=ax+b$
$a=m=\frac{-4}{3}$

$5=\frac{-4}{3}(-2)+b
$

$5=\frac{8}{3}+b$
$b=5-\frac{8}{3}$
$b=\frac{7}{3}$

$y=\frac{-4}{3}x+\frac{7}{3}$

Just as a different method (Bow)