# I Fınding the position of a point on the line

#### Arman777

Gold Member
Let us suppose we have a line $l_1 = ax + by + c = 0$ and we have a point P, $P(x_p, y_p)$ that is outside of this line. If we draw a perpendicular line from point $P$ to a point on the $l_1$. What would be the coordinates of this point ? I know there are many ways to do it. But I am looking for a single equation that can describe this point ($Q$) ? #### pasmith

Homework Helper
Have you considered using one of those methods to solve the problem, which should give you an expression for $Q$ in terms of $P$ and $l_1$?

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