Step by step
The question
Question: find the perimeter of the square with corners (−1, −1), (3, −1), (3, 3), (−1, 3).
square: (−1, −1), (3, −1), (3, 3), (−1, 3)
1 Plot the points
We put the corners on the grid.
Corner A is (−1, −1).
And so on.
We join them in order.
2 Find the side lengths
A B: the same y, so it goes across.
Its length is the bigger x minus the smaller: 3 minus −1 is 4.
= AB: 3 − (−1) = 4
Careful!
−1 is on the other side of 0.
Minus a negative is plus: 3 plus 1.
Careful: not 3 − 1 = 2 ✗
B C: the same x, so it goes up and down.
Its length is the bigger y minus the smaller: 3 minus −1 is 4.
= BC: 3 − (−1) = 4
3 Perimeter
The perimeter is the way round: all four sides.
= perimeter = all four sides
4 plus 4 plus 4 plus 4 is 16 units.
= perimeter = 4 + 4 + 4 + 4 = 16 units
4 Check
Let's check: opposite sides are the same.
So it is 2 times 4 plus 4: 2 times 8 is 16.
So the answer is right!
2 × (4 + 4) = 2 × 8 = 16
Let's look back.
First: plot the points.
Then: find the side lengths.
Then: perimeter.
Last: check.
Answer
= perimeter = 4 + 4 + 4 + 4 = 16 units