Plot the points:
Draw the line:
1.Find y when x=6
Draw a vertical line through 6 on the x-axis
From where the blue line crosses the green line draw a red horizontal
line
Look and see that the red horizontal line crosses the y-axis at -1.
So the answer is y = -1 when x = 6.
2. Find x when y=-1
We just got through showing that "when x = 6, y = -1". So just
turn that around and say "when y = -1, x = 6
3. Find the x-intercept.
We look and see where the green line crosses the x-axis.
We see it is one of the points we were given at the start. It is the point
(4,0)
The x-intercept is the point (4,0).
4. Find the slope of the line
We draw a horizontal blue line from the given point (0,2) rightward until
we are directly above the other given point (4,0) and then draw a
vertical red line from there down to the point (4,0), like this:
The horizontal blue line is 4 units long and goes right, so we assign it
the value +4. (If it had gone left we would have assigned it -4). The
vertical line is 2 units long and goes down, so we assign it the value -2.
(If it had gone up we would have assigned it the value +2).
vertical line's value -2
Slope = ------------------------- = ----- =
horizontal line's value +4
5. Find the equation of the line.
Substitute the slope for m.
Since the green line goes through (4,0), substitute 4 for
and 0 for . Leave x and y as they are:
Then simplify:
6. Find y when x =-2
Two ways.
First way.
---
1.Find y when x=-2
Draw a vertical line through -2 on the x-axis
From where the blue line crosses the green line draw a red horizontal
line
Look and see that the red horizontal line crosses the y-axis at 3.
So the answer is y = 3 when x = -2.
Second way:
Substitute -2 for x in the equation we found in 5
7. find x when y = -5
Two ways:
First way:
Draw a horizontal line through -5 on the y-axis:
Oh my! we have to make the graph wider so the red line will cross
the green line:
From where the red line crosses the green line we draw a blue vertical
line
Look and see that the blue vertical line crosses the x-axis at 14.
So the answer is x = 14 when y = -5.
Second way:
Substitute -5 for y in the equation we found in 5:
Multiply both sides by 2
8. Find the y intercept.
First way:
We look and see where the green line crosses the y-axis.
We see it is one of the points we were given at the start. It is the point
(0,2)
The y-intercept is the point (0,2).
Second way:
Substitute x=0 in the equation we found in 5:
So we substituted x=0 and got y=2 so the y-intercept is (0,2).
Edwin