Explanation:
The minimum number of points needed to draw a strait line graph is 2. However, 3 is better as one of them forms a check. They should all line up. If not then something is wrong.
Lets determine 2 points
The line will 'cross' the y axis at
x
=
0
and cross the x axis at
y
=
0
So we can determine these points (intercepts) by substitution.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For y-intercept set
x
=
0
giving:
y
=
2
x
.
.
+
2
y
=
(
2
×
0
)
+
2
→
y
=
2
So y-intercept is at the point
(
x
,
y
)
=
(
0
,
2
)
For x-intercept set
y
=
0
giving:
0
=
2
x
+
2
Subtract
2
from both sides
0
−
2
=
2
x
+
2
−
2
−
2
=
2
x
+
0
Divide both sides by
2
−
2
2
=
2
2
×
x
But
−
2
2
=
−
1
and
2
2
=
+
1
−
1
=
x
So the y-intercept is at the point
(
x
,
y
)
=
(
−
1
,
0
)