1 × 1 = 1 2 × 2 = 4 3 × 3 = 9 4 × 4 = 16 5 × 5 = 25
The square numbers are 1, 4, 9, 16, 25, …
You use an index of 2 to show square numbers.
12 = 1 22 = 4 32 = 9 42 = 16 52 = 25
You read 12 as ‘1 squared’ and you read 22 as ‘2 squared’.
42 = 16 is equivalent to 4 = √16, which is read as ‘4 is the square root of 16’.
The symbol for square root is √.
Cube root symbol: The symbol for cube root is ∛.
1 × 1 × 1 = 1 2 × 2 × 2 = 8 3 × 3 × 3 = 27
The cube numbers are 1, 8, 27, …
You use an index of 3 and write 13 = 1, 23 = 8, 33 = 27, …
You read 13 as ‘1 cubed’ and you read 23 as ‘2 cubed’.
You say ‘2 is the cube root of 8’, which is written as 2 = ∛8.
You can estimate the square roots of integers that are not square numbers.
1a. Copy and complete: $3^2 =$
1b. Copy and complete: $5^2 =$
1c. Copy and complete: $8^2 =$
1d. Copy and complete: $10^2 =$
1e. Copy and complete: $15^2 =$
2. An equivalent statement to $7^2 = 49$ is $\sqrt{49} = 7$. Write equivalent statements to your answers to Question 1.
3a. Find $\sqrt{36}$
3b. Find $\sqrt{81}$
3c. Find $\sqrt{121}$
3d. Find $\sqrt{144}$
4a. $1^3 =$
4b. $2^3 =$
4c. $3^3 =$
4d. $4^3 =$
4e. $5^3 =$
5. Write equivalent statements to your answers to Question 4, using cube root notation.
6a. Work out the integer closest to $\sqrt{15}$
6b. Work out the integer closest to $\sqrt{66}$
6c. Work out the integer closest to $\sqrt{150}$
7a. Show that $\sqrt{90}$ is between 9 and 10.
7b. Find two consecutive integers to complete: $\sqrt{180}$ is between … and …
7c. Find two consecutive integers to complete: $\sqrt[3]{90}$ is between … and …
8a. Use a calculator to find $17^2$.
8b. Complete this statement: $\sqrt{\,\boxed{\phantom{0}}\,} = 17$
9a. $\sqrt[3]{\boxed{\phantom{0}}} = 18$
9b. $\sqrt[3]{\boxed{\phantom{0}}} = 20$
9c. $\sqrt[3]{\boxed{\phantom{0}}} = 23$
9d. $\sqrt[3]{\boxed{\phantom{0}}} = 26$
10a. $\sqrt[3]{\boxed{\phantom{0}}} = 7$
10b. $\sqrt[3]{\boxed{\phantom{0}}} = 9$
10c. $\sqrt[3]{\boxed{\phantom{0}}} = 10$
10d. $\sqrt[3]{\boxed{\phantom{0}}} = 12$
11a. Show that 36 has nine factors.
11b(i). Find the factors of 9.
11b(ii). Find the factors of 16.
11b(iii). Find the factors of 25.
11c. Explain why every square number has an odd number of factors.
11d. Find a number that is not square and has an odd number of factors.
11e. Does every cube number have an odd number of factors? Give a reason.
11f. Investigate how many factors different square numbers have.
Question: What patterns can you find in the differences between consecutive square numbers and consecutive cube numbers?
Equipment: Pencil, paper, calculator (optional)
Square numbers:$1^2$, $2^2$, $3^2$, $4^2$, $5^2$, $6^2$
Differences:3, 5, 7, 9, 11
Cube numbers:$1^3$, $2^3$, $3^3$, $4^3$, $5^3$, $6^3$
Differences:7, 19, 37, 61, 91
Follow-up Questions:
12a(i). Work out: $\sqrt{1^3}$
12a(ii). Work out: $\sqrt{1^3 + 2^3}$
12a(iii). Work out: $\sqrt{1^3 + 2^3 + 3^3}$
12b. What do you notice about your answers to part a?
12c. Does the pattern continue with more cubes? Explain.
13a. Add the first three odd numbers and find the square root of the answer.
13b. Add the first four odd numbers and find the square root of the answer.
13c. Can you generalise the results of parts a and b?
13d. Look at this diagram. How is it connected to the earlier parts?

Don’t confuse $\sqrt{64}$ with $\sqrt[3]{64}$. The square root of 64 is $8$, but the cube root of 64 is $4$ — they are different operations with different results!
Now that you've explored square and cube numbers — and learned how to estimate their roots — you're ready to go deeper. You'll investigate what happens when roots involve negative numbers, discover why square roots can have two answers, and learn how these ideas help solve real equations.
52 = 25
This means that the square root of 25 is 5. This can be written as $\sqrt{25} = 5$.
This is the only answer in the set of natural numbers.
However (–5)2 = –5 × –5 = 25
This means that the integer –5 is also a square root of 25.
Every positive integer has two square roots, one positive and one negative.
5 is the positive square root of 25 and –5 is the negative square root.
No negative number has a square root.
For example, the integer –25 has no square root because the equation $x^2 = -25$ has no solution.
53 = 125
This means that the cube root of 125 is 5. This can be written as $\sqrt[3]{125} = 5$.
You might think –5 is also a cube root of 125.
However (–5)3 = –5 × –5 × –5 = (–5 × –5) × –5 = 25 × –5 = –125
So $\sqrt[3]{-125} = -5$
Every number, positive or negative or zero, has only one cube root.
Natural numbers: These are the counting numbers and zero.
14. Work out
a) $7^2$
b) $(-7)^2$
c) $7^3$
d) $(-7)^3$
15. Find
a) $\sqrt[3]{125}$
b) $\sqrt[3]{-27}$
c) $\sqrt[3]{1}$
d) $\sqrt[3]{8}$
16. Solve these equations:
a) $x^2 = 100$
b) $x^2 = 144$
c) $x^2 = 1$
d) $x^2 = 0$
e) $x^2 + 9 = 0$
17. Solve these equations:
a) $x^3 = 216$
b) $x^3 + 27 = 0$
c) $x^3 + 1 = 0$
d) $x^3 + 125 = 0$
18. Use the fact $27^2 = 9^3 = 729$ to find:
a) $\sqrt{729}$
b) $\sqrt{-729}$
c) $\sqrt[3]{729}$
d) $\sqrt[3]{-729}$
19. a) A calculator shows that $\sqrt{82} - \sqrt{(-8)^2} = 0$.
Explain why this is correct.
b) Find the value of $\sqrt[3]{4^3} - \sqrt[3]{(-4)^3}$. Show your working.
20. The square of an integer is 100.
What can you say about the cube of the integer?
21. The integer 1521 = $3^2 \times 13^2$
Use this fact to:
a) Find $\sqrt{1521}$
b) Solve the equation $x^2 = 1521$
22. a) How is $-5^2$ different from $(-5)^2$?
b) What is the difference between $-5^3$ and $(-5)^3$?
23. a) Show that $3^2 + 4^2 = 5^2$
b) Are these statements true or false? Give a reason for your answer each time:
i) $(-3)^2 + (-4)^2 = (-5)^2$
ii) $(-13)^2 = 12^2 + (-5)^2$
iii) $8^2 = -10^2 - 6^2$
c) Show your work to a partner. Do they find your explanation clear?
Question: How can we find two solutions to quadratic equations like $x^2 + x = n$? What patterns do you notice?
Equipment: Pencil, paper, calculator (optional)
Method:
Follow-up Questions:
24. a) Copy and complete this table.
| $x$ | $x - 1$ | $x^3 - 1$ | $x^2 + x + 1$ |
|---|---|---|---|
| 2 | 1 | 7 | |
| 3 | 2 | 13 | |
| 4 | |||
| 5 |
b) What pattern can you see in your answers?
c) Add another row to see if the pattern is still the same.
d) Add three rows where $x$ is a negative integer.
Is the pattern still the same if $x$ is a negative integer?
| $x$ | $x - 1$ | $x^3 - 1$ | $x^2 + x + 1$ |
|---|---|---|---|
| 2 | 1 | 7 | 7 |
| 3 | 2 | 26 | 13 |
| 4 | 3 | 63 | 21 |
| 5 | 4 | 124 | 31 |
25. Any number that can be written as a fraction is a rational number.
Examples are: $7\frac{3}{4}, -12, \frac{18}{25}, 6, \frac{1}{15}, -2\frac{9}{10}$
Here is a list of six numbers:
$5,\quad -\frac{1}{5},\quad -500,\quad 16,\quad -4.8,\quad 99\frac{1}{2}$
Rational numbers: Integers and fractions are both part of the set of rational numbers.
26. This Venn diagram shows the relationship between natural numbers and integers.
N stands for natural numbers and I for integers.
Integers and rational numbers: Remember, all integers are part of the rational number set.

b) Write each of these numbers in the correct part of the diagram:
$1,\ -3,\ 7,\ -12,\ 41,\ -100,\ 2\frac{1}{2}$
c) Add another circle to your Venn diagram to show rational numbers.
d) Add these numbers to your Venn diagram:
$-8\frac{3}{7},\quad \frac{3}{5},\quad 0,\quad 6.3,\quad -\frac{10}{3}$