8920370
Description
Flashcards by Liffey Farrell, updated more than 1 year ago
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Created by Liffey Farrell
almost 7 years ago
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| Question | Answer |
| Vertical and Horizontal lines: 'x=a' and 'y=a' x=a is a vertical line through 'a' on the x-axis y=a is a horizontal line through 'a' on the y-axis | The Main Diagonals: 'y=x' and 'y=-x' y=x is the main diagonal that goes uphill from left to right y=-x is the main diagonal that goes downhill from left to right |
| Other Lines Through the Origin: 'y=ax' an 'y=-ax' y=ax and y=-ax are the equations for a sloping line through the origin. The value of 'a' (known as the gradient) tells you the steepness of the line. The bigger the 'a' is, the steeper the slope. A minus sign tells you the slope is downhill | Learn to spot straight lines from their equations: All straight-line equations just contain 'something x, something y and a number' |
| Straight lines: x - y = 0 y = 2 + 3x 2y - 4x = 7 4x - 3 = 5y | Not straight lines: y = x3 + 3 1/y + 1/x = 2 x2 = 4 - y xy + 3 = 0 |
| You might be asked to draw the graph of an equation in the exam. 1) Choose 3 values of x and draw a table 2) Work out the corresponding y-values 3) Plot the coordinates, and draw the line | Doing the 'Table of Values': Draw the graph of y = 2x -3 1) Choose 3 easy x-values for your table Use x-values from the grid you're given. Avoid negative ones if you can. |
| 2) Find the y-values by putting each x-value into the equation When x = 0, y = 2x -3 = (2x0) - 3 = -3 y = -3 When x = 4 y = 2x -3 = (2x4) -3 = 5 | 3) Plot each pair of x- and y- values from your table. The table gives the coordinates e.g. (0, -3) and (4, 5) Now draw a straight line through your points. If a point looks wrong, check the y-values you worked out in the table, and that you've plotted the points correctly |
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