IB DP Maths: AA SL复习笔记2.1.1 Equations of a Straight Line
How do I find the gradient of a straight line?
- Find two points that the line passes through with coordinates (x1, y1) and (x2, y2)
- The gradient between these two points is calculated by
-
- This is given in the formula booklet
- The gradient of a straight line measures its slope
- A line with gradient 1 will go up 1 unit for every unit it goes to the right
- A line with gradient -2 will go down two units for every unit it goes to the right
What are the equations of a straight line?
How do I find an equation of a straight line?
- You will need the gradient
- If you are given two points then first find the gradient
- It is easiest to start with the point-gradient form
- then rearrange into whatever form is required
- multiplying both sides by any denominators will get rid of fractions
- then rearrange into whatever form is required
- You can check your answer by using your GDC
- Graph your answer and check it goes through the point(s)
Exam Tip
Worked Example
Parallel Lines
How are the equations of parallel lines connected?
- Parallel lines are always equidistant meaning they never intersect
- Parallel lines have the same gradient
Worked Example
Perpendicular Lines
How are the equations of perpendicular lines connected?
- Perpendicular lines intersect at right angles
- The gradients of two perpendicular lines are negative reciprocals
Worked Example
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