Zero on the axes
On the x-axis the second number is 0.
On the line
On Shalini's floor map, point B sits right on the x-axis wool. It is neither above the line nor below it.
B lies exactly on the x-axis. What do you think its y-coordinate is?
What this lesson covers
The idea
A point on the x-axis has coordinates (x, 0) and lies right of O if x is positive, left if negative; a point on the y-axis is (0, y), above O if y is positive, below if negative.
On the line
On Shalini's floor map, point B sits right on the x-axis wool. It is neither above the line nor below it.
B lies exactly on the x-axis. What do you think its y-coordinate is?
- 0
- 1
- The same as its x-coordinate
Slide along the axes
Slide P onto the axes and watch the two numbers.
Zero on an axis
A point on the x-axis has coordinates (x, 0). It lies right of O if x is positive and left of O if x is negative. A point on the y-axis has coordinates (0, y). It lies above O if y is positive and below O if y is negative.
- Point | Where it is | Coordinates
- B | on the x-axis, 4.5 units right of O | (4.5, 0)
- G | on the y-axis, 4.5 units down from O | (0, −4.5)
- H | on the y-axis, 4 units above O | (0, 4)
Notes
On the x-axis a point is (x, 0). On the y-axis a point is (0, y).
Check yourself
Which point lies on the x-axis?
A point on the x-axis is 7 units to the left of O. Its coordinates are (x, 0). What is x?
Answer: -7
Left of O is negative, so x = −7 and the point is (−7, 0).
Point Q is on the y-axis, 4 units above O. Its coordinates are…
Where does the point (−2, 0) lie?
- (0, 5). The first number is 0, so (0, 5) is on the y-axis.
- (5, 0) — correct. Yes. The second number is 0: it is on the x-axis, 5 units right of O.
- (5, 5). 5 across and 5 up: that point is not on either axis.
- (4, 0). (4, 0) is on the x-axis. Q is on the y-axis, so the first number is 0.
- (0, 4) — correct. Yes. On the y-axis the first number is 0, and 4 units above O is +4.
- (0, −4). −4 is 4 units below O. Q is above O.
- (4, 4). (4, 4) is not on an axis.
- On the x-axis, left of O — correct. Yes. The second number is 0, so it is on the x-axis; −2 means left of O.
- On the y-axis, below O. The second number is 0, so it is on the x-axis, not the y-axis.
- On the x-axis, right of O. −2 is negative: left of O.
- On the y-axis, above O. It is on the x-axis, because the second number is 0.