2.4 Writing Equations of Lines
In this lesson you will: Write linear equations.
Writing an Equation of a Line You can write the equation of a line using one of the following handy-dandy formulas: Slope-Intercept form: (Given the slope m and the y-intercept b) use this equation): Point-Slope Form: (Given the slope m and a point (x1,y1), use this equation): In calculus we consider this formula to be one of our “best friends.” Two Points: (Given two points (x1,y1) and (x2,y2), use the equation) Use this formula to find the slope m, then use the point-slope form with this slope and either of the given points to write an equation of the line.
Write the equation of the line shown: The y – intercept is -2 The slope is 3/2 y = (3/2)x-2
And finally simplify to y = (-1/2)x+4 Write the equation of the line that passes through (2,3) and has slope -1/2. Use the point-slope formula: y-3=(-1/2)(x-2) And finally simplify to y = (-1/2)x+4
Write the equation of the line that passes through (3,2) and is a) perpendicular and b) parallel to y = -3x + 2. The parallel line will have slope -3 and the perpendicular line will have slope 1/3. Perpendicular Parallel y=(1/3)x+1 y-2=-3(x-3) y = -3x+11 y-2=(1/3)(x-3)
Write the equation of the line that passes through (-2,-1) and (3,4) First determine the slope: You now know the slope and can use either of the given points in the point-slope formula. Would you get the same answer if you used either given point? y = x + 3