1819 H2Y §3.Refresh

• Wiskunde
• Middelbare school
• havo
• Leerjaar 2

CH3 Roots

What does it mean when you SQUARE a number?

Recap: Squaring

Squaring a number means you multiply that number with itself.

         The square of 5 is 25, because

For positive numbers you can think of calculating

the area of a square when you know the length

of the sides. (That is why we call it squaring)

Recap: Squaring

You can also square fractions, decimal numbers and negative numbers, when squaring fractions  and negative numbers you use brackets:

The square of      :

The square of 0.4:

The square of -7:

Recap: Squaring

Careful with negative signs!!!

Calculate

(−9)​2​​=

1. -18
2. 18
3. -81
4. 81

Recap: divisors and prime numbers

Divisors are whole numbers that you can divide a given number by that give a whole number as a result.

The divisors of 20 are 1, 2, 4, 5, 10 and 20.

(1x20=20, 2x10=20, 4x5=20)

Prime numbers are whole numbers whose only divisors are 1 and itself. The first five prime numbers are 2, 3, 5, 7 and 11

Recap: Rounding off

When rounding off a number, take the following steps

1) decide to how many decimal places you want to round off

2) look at the next decimal. If this is a 0, 1, 2, 3 or 4, leave the last decimal as it is. If this is a 5, 6, 7, 8, 9, add 1 to the last decimal.

5.62984

To whole numbers: 6                          To 3 decimal places: 5.630

To 1 decimal place: 5.6                      To 4 decimal places: 5.6298

To 2 decimal places: 5.63

Recap: perimeter

The perimeter is the lengths of all edges of a

plane figure added up.

The perimeter of this triangle is 3 + 4 + 5 = 12

Recap: writing formulas shorter

You can write formulas shorter by combining like terms.

Like terms are terms with the same variable, to the same power.

Write down any questions you have.

Homework Tuesday

• Bring a calculator
• Make and correct from §3.Refresh (page 90-91):
  

                 R1, R2, R4, R5, R6, R7, R8 (so not R3)