+

2.5 Writing equations of linesObjective: Write linear equations.

+Writing an equation of a line

Slope-Intercept Form: given the slope m and the y-intercept b, use slope-intercept form: y = mx+b

Point-Slope Form: given the slope m and a point (x1,y1), use point- slope form: y-y1 = m(x-x1)

+Examples

Write an equation of the line given slope and y-intercept.

1. m=3, b=1

2. m= -2, b= -4

3. m= ½ , b= -5

+Write the equation of a line when given a graph.

+Examples

Write an equation of the line shown.

y = __________y = ___________ y = ___________

+Point-Slope Form

+examples

Write an equation of the line that passes through the given point and as the given slope. Write your equation in slope-intercept form.

1. (4,2), m= -1/4

2. (-1,3), m= 2

3. (4,-5), m= -3

+Examples

4. (-2,4), m=5

5. (-3,-3), m= 2/3

+

+

Write equations of parallel lines

Write an equation of the line that passes through (-1,4) and is parallel to the line y = -2x + 5

+Write equations of perpendicular lines

Write an equation of the line that passes through (-1,4) and is perpendicular to the line y = -2x + 5

+ Write an equation of the line described.

1. Passes through (-6,-5); parallel to y = -x + 2

2. Passes through (-6, -5); perpendicular to y = -x + 2

+ Write an equation of the line described

1. Passes through (-2,3); parallel to y =4x – 1

2. Passes through (-2,3); perpendicular to y=4x – 1

+Write a linear Model

In 1995 there were only 6 California condors living in the wild (all in California). In 2006 there were 138 California condors living in the wild (in California, Arizona, and Mexico). Write a linear model that represents the number of California condors living in the wild between 1995 and 2006.