2.4+Write+Equations+of+lines

**Point-Slope Form - An equation of a line written in the form y-y, = m(x-x1) where the line passes through the point(x1,y1) and has a slope of m.**

 * Point Slope Form**
 * y- y1= m(x-x1) Use point slope form.**
 * y- 4= -3(x-5) Substitute for m, x1, and y1.**
 * y- 4= -3x + 15 Distributive property**
 * y= -3x + 19 Write in slope-intercept form.**



** Point Slope Form: ** [used when you know, or can find, a point on the line **//(x//1//, y//1//)//**, and the slope, **//m//**.] **Horizontal Line Form:** **//y// = 3** (or any number) Lines that are horizontal have a slope of zero. They have "run", but no "rise". The rise/run formula for slope always yields zero since rise = 0. //y = mx + b// //y =// 0//x// + 3 //y// = 3 **Vertical** **Line Form:** **//x// = -2** (or any number) Lines that are vertical have no slope (it does not exist). They have "rise", but no "run". The rise/run formula for slope always has a zero denominator and is undefined. Here is a link for a further in-depth analysis of Writing equations of lines. []
 * Equations of line can take on several forms: **
 * Slope Intercept Form: ** [used when you know, or can find, the slope, **//m//**, and the //y//-intercept, **//b//**.] //**y**// **=//mx + b//**