Pre-Algebra Math Grade 7 : Pre-Algebra Math Grade 7 Chapter 6: Writing & Simplifying Expressions Lesson 3: Combining Like Terms page 131
Vocabulary : The parts of algebraic expression that are separated by an + or – sign are called terms.
Example, there are 3 terms in this expression:
2x + 6 - 4y
Like terms are terms which have the same variable raised to the same power. Example, 3a, 2a x2, 4x2 n3, 7n3
When you combine like terms in an expression your are writing the simplest form. Vocabulary
An old saying in Mathematics “You can’t add apples and oranges” : To combine like terms, add or subtract the numerical parts of the terms. Example,
7x + 2x + 5 =
9x + 5
7x + 2x +5 = 9x +5
9x + 5 is the simplest form An old saying in Mathematics “You can’t add apples and oranges”
Class work : Class work 4x – x + 5 =
3x + 5
If x = 2, evaluate the above expression
3x + 5 = 3(2) + 5 = 6 + 5 = 11
How many terms does this expression have?
4x – x + 5
3 terms
And this expression? 3x + 5
2 terms
Combine like terms or Simplify 3p – 2p + 6 -2 + p : Combine like terms or Simplify 3p – 2p + 6 -2 + p 3p – 2p + p + 6 – 2
(3p – 2p + p) + (6 – 2)
2p + 4 Commutative Property
Associative Property
Order of Operation 3p – 2p + 6 – 2 + p = 2p + 4
Class workSimplify : Class workSimplify 7n2 + 18 – 2 + n2
7n2 + n2 + 18 – 2
(7n2 + n2)+ (18 – 2)
8n2 + 16
Simplify 3(s - 4) + 6s : Simplify 3(s - 4) + 6s 3(s – 4) + 6s
3s – 12 + 6s
3s + 6s – 12
9s – 12
3(s – 4) + 6s = 9s - 12 Distributive Property Commutative Property
Class workSimplify 5q – 4 – 6q : Class workSimplify 5q – 4 – 6q 5q – 6q – 4
-q – 4
5q- 4 - 6q = -q - 4 Rule for adding/subtracting integers Commutative Property
Class work : Class work Simplify 18y + 6z – 15y – 3z
18y – 15y + 6z – 3z
3y + 3z
Simplify 2y + 3(2x + y) – 5x
2y + 6x + 3y – 5x
2y + 3y + 6x – 5x
5y + x
Homework due Wednesday 30th Dec.P27 : Homework due Wednesday 30th Dec.P27 Don’t forget H.W due today P25/26 !!