Copy the figure and mark S and Q in your diagram. Mark any point P in Quadrant I and any point R in Quadrant III, and write down their coordinates.
Step-by-step solution
Idea: To plot (x, y), start at O, move x units along the x-axis (right if positive, left if negative), then y units parallel to the y-axis (up if positive, down if negative).
- S (3, −5): from O move 3 units right, then 5 units down. Mark S; it lies in Quadrant IV.½ mark
- Q (−5, 3): from O move 5 units left, then 3 units up. Mark Q; it lies in Quadrant II.½ mark
- P in Quadrant I: both coordinates must be positive. Choose P (4, 2): 4 right, 2 up.½ mark
- R in Quadrant III: both coordinates must be negative. Choose R (−3, −4): 3 left, 4 down.½ mark
- Any other choice is correct as long as P has both coordinates positive and R has both coordinates negative (for example P (1.5, 6), R (−7, −2)).
Check: Signs: P (4, 2) is (+, +), Quadrant I ✓; R (−3, −4) is (−, −), Quadrant III ✓.
Answer to write in the exam
S (3, −5): 3 units right, 5 units down → Quadrant IV
Q (−5, 3): 5 units left, 3 units up → Quadrant II
P in Quadrant I (both coordinates positive): P (4, 2)
R in Quadrant III (both coordinates negative): R (−3, −4)
Common mistakes that cost marks
- Plotting (3, −5) by going 3 up and 5 left. The first number is always the move along the x-axis.
- Putting S and Q in the same place because they use the same numbers. (3, −5) and (−5, 3) are different points in different quadrants.
- Choosing R (−3, 4) for Quadrant III. Only one coordinate is negative there, so that point is in Quadrant II.
How this can come in the exam
Which of these points lies in Quadrant III?
- (−4, 2)
- (3, −1)
- (−2, −6)
- (0, −5)
Show answer
(C) (−2, −6)
Only (−2, −6) has both coordinates negative. (0, −5) is on the y-axis.
Plot K (−3, 0), N (−3, 2) and L (0, 2). Name the figure OKNL, where O is the origin, and find its area.
Show answer
OK runs 3 units along the x-axis, KN goes 2 units up, NL 3 units right, LO 2 units down; all angles are right angles. OKNL is a rectangle 3 by 2 (1 mark), area = 3 × 2 = 6 square units (1 mark).Try one yourself
Write a point in each quadrant whose two coordinates add up to 1. Is this possible in every quadrant?
Show answer
Quadrant I: (0.5, 0.5); Quadrant II: (−2, 3); Quadrant IV: (3, −2). Quadrant III is impossible: there both coordinates are negative, so their sum is negative, never 1.
More questions like this
- 1. What is the x-coordinate of a point on the y-axis?
2. Is there a similar generalisation for a point on the x-axis?
3. Does point Q (y, x) ever coincide with point P (x, y)? Justify your answer.
4. If x ≠ y, then (x, y) ≠ (y, x); and (x, y) = (y, x) if and only if x = y. Is this claim true? - Place Reiaan’s rectangular study table with three of its feet at the points (8, 9), (11, 9) and (11, 7).
- If the bathroom door has a hinge at B1 and opens into the bedroom, will it hit the wardrobe? Are there any changes you would suggest if the door is made wider?
- Look at Reiaan’s bathroom.
- Other rooms in the house: