I can do parallel lines, but not perpendicular
find the equation of the straight line in form ax + by + c = o which:
passes through (1,4) and is perpendicular to 5y = x + 2
thanks
First we need the gradient f the line:
$\displaystyle y = mx + c$
$\displaystyle y = 1/5x + 2/5$
Therefore we now know the gradient of the given line is 1/5.
So the gradient of the perpendicular line must be -5.
Putting this into the equation of the line we are finding, we get:
$\displaystyle y = -5x + c$
$\displaystyle c$ is the y intercept, which is what we will need to find.
$\displaystyle c = y + 5x$
Now, we just need to put the coordinates into the equation to find $\displaystyle c$.
$\displaystyle c = 4 + 5(1)$
$\displaystyle c = 4 + 5$
$\displaystyle c = 9$
We now have our equation
$\displaystyle y = -5x + 9$
(can also be written as: $\displaystyle y = 9 - 5x$)
//j0k3r