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How well can you write the equations of lines that are parallel or perpendicular to each other?

When you know the equation of one line, you can use its slope and other given information to write an equation of a line that is parallel or perpendicular to it. The steps for completing this process are shown in the table below.

  1. Name the slope of the line you were given.
  2. Determine the slope of the line you need to write an equation for.
  3. Use the slope and the information in the problem to write an equation in point-slope form.
  4. Rewrite the point-slope equation in slope-intercept form, if necessary.

How well can you write equations for lines that are parallel or perpendicular to a given line? Use the activity below to practice. Read the information on each tab. Write an equation for a line that is either parallel or perpendicular to the line represented by the given equation. Then, check your answer. Remember to pay close attention to which form you are asked to give your answer in.

Write the equation of a line that is parallel to y=2x+3, if the parallel line passes through the ordered pair (4,1). Express your final answer in slope-intercept form.

y=2x9

If you need help arriving at this answer, click the Solution button.

Step 1: Name the slope of the line you were given.

The equation y=2x+3 is expressed in slope-intercept form.

The slope is m=2.

Step 2: Determine the slope of the line you need to write an equation for.

You need to write an equation of a line that is parallel to y=2x+3.

The new equation must have a slope of m=2 because parallel lines have identical slope values.

Step 3: Use the slope and the information in the problem to write an equation in point-slope form.

The slope of the parallel line will be m=2. The ordered pair the parallel line passes through is (4,1).

y(1)=2(x(4))

Step 4: Rewrite the point-slope equation in slope-intercept form, if necessary.

y(1)=2(x(4))

y+1=2(x+4)

y+1=2x8

y=2x9