GradientSmall.jpgDefinitions

A Reminder
  • Cartesian graph is a graph drawn on a number plane with two perpendicular axes, the x-axis and the y-axis.
  • Coordinates are the ordered pairs that locate points on a graph. The first number is the distance along the x-axis (horizontal) and the second number is the distance along the y-axis (vertical).
  • Each point is located by an ordered pair. e.g. (x, y), (3, 4)
  • The origin is the point where the two axes intersect. The origin has coordinates of (0, 0).
  • The intercepts of a graph are the points where the graph cuts the x-axis and y-axis.

 

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Gradient

The gradient of a straight line is a measure of its slope.

The gradient, m is defined as:

Y9_Gradients_02.gif

=Y9_Gradients_04.gif

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Gradients can be given as integers, fractions or decimals.

 

Types of gradient

 

A line sloping upwards from left to right has a positive gradient.

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m is positive

A line sloping downwards from left to right has a negative gradient.

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m is negative

Parallel lines have the same gradient.

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m1 = m2

horizontal line has a gradient of 0.

m = 0

The gradient of a vertical line is undefined.

m is undefined

 

Click Here for practice at calculating gradients.

 

Example
Answer

What is the gradient of the line below?

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What is the gradient of the line joining the points 
(1, 2) to (4, 5)?

Draw a diagram

Y9_Gradients_10.gif

 

What is the gradient of the line joining the points 
(2, -3) to N (-3, 5)?

Draw a diagram

Y9_Gradients_11.gif