3.3.2
Straight Line Graphs
Straight Line Graphs
Straight Line Graphs
Any straight line can be written as y = mx + c.


y = mx + c
y = mx + c
- m is the gradient of the line
- c is the y-intercept (the height of the point where the line crosses the y axis.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Parallel lines have the same gradient
Parallel lines have the same gradient
- y = 3x + 2 and y = 3x - 4 are parallel lines because they have the same gradient (3).
Gradient and y-intercept of a Line
Gradient and y-intercept of a Line
A line y = mx + c has gradient m and y-intercept c.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
y-intercept
y-intercept
- The point where a line crosses the y-axis is called the y-intercept.


Gradient
Gradient
- To calculate the gradient (slope) of a line, use 2 co-ordinates (A and B):
- gradient = change in y ÷ change in x
- where change in y = (yA - yB) and change in x = (xA - xB)
Midpoint of a Line
Midpoint of a Line
The midpoint of a line is the point that lies the same distance from each of the endpoints.


Midpoint
Midpoint
- To calculate the coordinates of the midpoint between points A and B, work out the horizontal distance between A & B and add half of this to the x-coordinate of A.
- This is the x-coordinate of the midpoint.
- Do the same for the vertical distance to get the y-coordinate.


Midpoint formulae
Midpoint formulae
- The coordinates of the midpoint of a line AB are given by the formulae above.
1Numbers
1.1Integers
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2Equations, Formulae & Identities
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3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
Jump to other topics
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
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