1 / 6

Graphing straight lines

Graphing straight lines. The gradient-intercept form of a straight line is: y = mx + b where m is the gradient and b is the y -intercept. If the line is not in this form, I would change it to this form. How I use this form to plot a line: Plot the y -intercept ( b )

zared
Télécharger la présentation

Graphing straight lines

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Graphing straight lines The gradient-intercept form of a straight line is: y = mx + b where m is the gradient and b is the y-intercept. If the line is not in this form, I would change it to this form. How I use this form to plot a line: • Plot the y-intercept (b) • Move up by the “rise” • Move across by the “run” • Plot the 2nd point • Join the two points to form the line. Alternate method • Complete a table of values • Use at least three values.

  2. Example 1  Graph the line y = 2x + 1 Method 1 • Plot the point (0, 1)   • As the gradient is 2, this is 2/1. • Move up by 2 • Move across 1 • Plot the 2nd point • Join the two points to form the line. Method 2 • Complete a table of values • Use at least three values. y = 2x + 1 –1 0 1 –1 1 3

  3. Example 2 Graph the line 3x + 2y + 4 = 0  Method 1 • Change to y = mx + b 3x + 2y + 4 = 0 2y = –3x – 4 y = –3x/2– 2 • Plot the point (0, –2)   • Move down by 3, as the gradient is negative • Move across 2 • Plot the 2nd point • Join the two points to form the line. Method 2 • Change to y = mx + b y = –3x/2– 2 Pick “nice” values for x. Multiples of 2, as the denominator is 2 –2 0 2 1 –2 –5

  4. Graphing straight linesLines parallel to the axes The line x = a is parallel to the y-axis, the y-values change but x always equals a. Example 3 Graph the line x = 3 The line y = b is parallel to the x-axis, the x-values change but y always equals b. Example 4 Graph the line y = –2

  5. Does a point lie on the line? A point lies on a line if its coordinates satisfy the equation of the line. OR Substitute the point into the equation of the line; if LHS = RHS, the point lies on the line. if LHS ≠ RHS, the point is not on the line Example 5 Does the point (2, 5) lie on the line y = 3x + 1? 5 = 3(2) + 1 5 ≠ 7  (2, 5) IS NOT on the line y = 3x + 1. Example 6 Does the point line 3x + 2y – 22 = 0 pass through the point (4, 5)? 3(4) + 2(5) – 22 = 0 0 = 0  The line 3x+2y–22 = 0 passes through the point (4, 5).

  6. Today’s work Exercise 10:05 Q1-4 Yesterday’s work Exercise 8:03 Q1 a, c, e…o, p, q & r, Q2 & 3 all

More Related