1718 WH3X CH4 Lesson 3

• Wiskunde
• Middelbare school
• havo
• Leerjaar 3

Which exercises from the homework should I discuss on the board?

Linear formulas

y = ax + b is the general form of a linear formula.
In this formula a is the gradient and b is the y-intercept.

The corresponding graph is an increasing or decreasing straight line.
The corresponding table has a regular increase/decrease in the bottom row if the top row contains consecutive whole numbers.

Linear formulas

y = ax + b is the general form of a linear formula.
In this formula a is the gradient and b is the y-intercept.

You can make a formula when  you are given:
- a graph
- a table
- the coordinates of two points on the graph

Gradient

Gradient in a graph:
If you increase 1 step on
the horizontal axis, the
corresponding increase/decrease
on the vertical axis is the gradient.

gradient f = 2
gradient g = -1.5

Gradient

Gradient in a table:
If you increase 1 step in the top row,
the corresponding increase/decrease
in the bottom row is the gradient.

gradient k = 2.5
gradient m = -3

Gradient

Gradient from 2 given points on the graph:                     line q passes through
Use this formula to calculate the gradient:                           points P(3, -4) and
                                                                                                                    R(9, -2).




gradient q =

Gradient

If two graphs have the same gradient, the graphs are parallel.

Y-intercept

Y-intercept in a graph:
The vertical coordinate of the
point of intersection with the
vertical axis is the y-intercept.

y-intercept f = -4
y-intercept g = 8

Y-intercept

Y-intercept in a table:
The value in the bottom row when
the value in the top row is zero is
the y-intercept.

y-intercept k = 4.5
y-intercept m = 50

Y-intercept

Y-intercept from 2 given points on the graph:              line q passes through
Fill in gradient, and the x- and y-coordinate of                  points P(3, -4) and
one of the points into the general linear formula.           R(9, -2). (Gradient = 1/3)
Calculate the y-intercept.



y-intercept q = -5

Y-intercept

If two graphs have the same y-intercept, they intersect the y-axis at the same point.

Formulas

If you know the gradient and the y-intercept, you can fill in the general linear formula (y=ax+b) to find the formula.
gradient f = 2         y-intercept f = -4
gradient g = -1.5    y-intercept g = 8
gradient k = 2.5     y-intercept k = 4.5
gradient m = -3      y-intercept m = 50
gradient q = 1/3     y-intercept q = -5

Homework Tuesday

§4.1, make and correct:
All key exercises: 3, 4, 5, 6
At least 1 basic exercise: 1, 2

Any (useful) questions/comment?