Solving equations involving parallel and perpendicular lines examples

Solving equations involving parallel and perpendicular lines examples Solving equations involving parallel and perpendicular lines examples

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11. Example – Find the slope of a line perpendicular to the line whose equation is y – 3x = 2. y – 3x = 2 y = 3x + 2 Write equation in slope-intercept form. The slope of the given line is 3. 3(m) = –1 1 m = − 3 Let m stand for the slope of the perpendicular line. The slope of any line perpendicular to the given line is 1 − 3 12. Example – Find the slope of a line perpendicular to the line whose equation is 3x – 7y = 6. 3x – 7y = 6 3 6 y = x − 7 7 Write equation in slope-intercept form. The slope is 7 3 3 (m) = –1 7 7 m = − 3 Let m stand for the slope of the perpendicular line. The slope of any line perpendicular to the given line is 7 − 3 Solving Equations Involving Parallel and Perpendicular Lines www.BeaconLC.org©2001 September 22, 2001 4

13. Example – Find an equation of the line that passes through (4, 6) and is perpendicular to the line whose equation is y = 3 2 x + 5. The slope of the given line is 3 2 . 2 (m) = –1 3 3 m = − 2 Use (4, 6) and the slope y = mx + b 3 6 = ( − )(4) + b 2 12 = b Let m stand for the slope of the perpendicular line. 3 − to find the y-intercept. 2 The y-intercept is 12. An equation of the line is y = 3 − x + 12 2 This could be written 3x + 2y = 24 14. Example – Find an equation of a line passing through (–1, –1) and is perpendicular to x + y = 6. y = –x + 6 The slope of the given line is –1. –1 (m) = –1 Let m stand for the slope of the perpendicular line. m = 1 Use (–1, –1) and the slope 1 to find the y-intercept. y = mx + b –1 = (1)( –1) + b The y-intercept is 0. 0 = b An equation of the line is y = x This could be written x – y = 0 Solving Equations Involving Parallel and Perpendicular Lines www.BeaconLC.org©2001 September 22, 2001 5

13. Example – Find an equation of the line that passes through (4, 6) <strong>and</strong> is<br />

<strong>perpendicular</strong> to the line whose equation is y = 3<br />

2 x + 5.<br />

The slope of the given line is 3<br />

2 .<br />

2 (m) = –1<br />

3<br />

3<br />

m = −<br />

2<br />

Use (4, 6) <strong>and</strong> the slope<br />

y = mx + b<br />

3<br />

6 = ( − )(4) + b<br />

2<br />

12 = b<br />

Let m st<strong>and</strong> for the slope of the <strong>perpendicular</strong> line.<br />

3<br />

− to find the y-intercept.<br />

2<br />

The y-intercept is 12.<br />

An equation of the line is y =<br />

3<br />

− x + 12<br />

2<br />

This could be written 3x + 2y = 24<br />

14. Example – Find an equation of a line passing through (–1, –1) <strong>and</strong> is<br />

<strong>perpendicular</strong> to x + y = 6.<br />

y = –x + 6 The slope of the given line is –1.<br />

–1 (m) = –1<br />

Let m st<strong>and</strong> for the slope of the <strong>perpendicular</strong> line.<br />

m = 1<br />

Use (–1, –1) <strong>and</strong> the slope 1 to find the y-intercept.<br />

y = mx + b<br />

–1 = (1)( –1) + b The y-intercept is 0.<br />

0 = b<br />

An equation of the line is y = x<br />

This could be written x – y = 0<br />

<strong>Solving</strong> Equations Involving Parallel <strong>and</strong> Perpendicular Lines www.BeaconLC.org©2001 September 22, 2001<br />

5

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