8.Write+equations+of+Lines+when+given+two+points+&+Write+equations+of+lines+from+a+graph

Write and Graph Equations of Lines (see 3.5) //Meaghan C., Cassie O., Emily W., Ema B. //

**//3 Necessary Formulas://** // The formula for finding slope is: // // m= __ y2-y1 __// x2-x1 EXAMPLE: Say we wanted to find the slope of (2,0) and (4,2). __ m=0-2 __ 2-4 __ m=-2 __ -2
 * 1) //**Slope:** When the points are already known (for example, you already know the measure of x1, y1, x2, and y2). This is how you will find the slope, “m”, quickly and easily. Just plug in the numbers to their respective spots. //
 * First choose your “x1” and “y1”. In this case, x1 is 4 and y1 is 2
 * Choose “x2 and y2”. In this case, 2 and 0.
 * Plug the numbers into the equation:
 * Subtract:
 * Divide: m=-1
 * The slope “m” is -1. This is how to find slope with the slope formula.


 * 1) //**Slope-Intercept:** When you already know the slope, whether it is given or it has been found using the formula above, you can plug it into the formula **y=mx+b** to find the equation of the line. “m” is the slope, and “b” is the y-intercept. The slope-intercept equation is y=mx+b. //
 * 2) // **Point-Slope:**  for a given point (x 1, y 1 ) and slope, “m”;  //

**//(y-y1)=m(x-x1)//** __**//SLOPE//** __ **Example Problem** || Find the slope of the line segment joining the points **( 1, - 4 )** and **( - 4, 2 )**. ||

**Solution** Label the points as //**x**//**1** **= 1**, //**y**//**1** **= - 4**, //**x**//**2** **= -4**, and //**y**//**2** **= 2**. To find the slope //**m**// of the line segment joining the points, use the slope formula : So, //m// = - 6 /5. **//http://cs.selu.edu/~rbyrd/math/slope///** //**__SLOPE-INTERCEPT__**// //y = mx + b// (–6) = (4)(–1) + //b// –6 = –4 + //b// –2 = //b// Then the line equation must be " **//y// = 4//x// – 2** ". [] y=mx+b (6)=(6)(1)+b 6=6+b 1=b  //**__Y-INTERCEPT__**// definition/ The //y//-coordinate of the point where a line intersects the //y//-axis is the //y//-intercept of that line. > Find the //y//-intercept of the line shown in the graph. > > **Choices:** > A. - 3 > B. 0 > C. 3 > D. 1 > **Correct Answer: A** > **Solution:** > **Step 1:** The y-coordinate of the point where a line intersects the //y//-axis is the //y//-intercept of that line. > **Step 2:** The graph of the line crosses the //y//-axis at (0, - 3). > **Step 3:** So, the //y//-intercept of the line is - 3. []

__**X-Intercept**__ Using the above graph, what is the place where the line crosses the x-coordinate?
 * a. -2**
 * b. -3**
 * c. 3**
 * d. 7**
 * CORRECT ANSWER: 3.** See where the line goes through the x-axis? That's where the x-coordinate is. It's always going to be on that horizontal line, never on the vertical line -- the vertical line is the Y-axis.