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3.2.4 Using Generic Rectangles to multiply
You have been using algebra tiles and the concept of area, Punnett Squares and the foil method to multiply
polynomial expressions. Today you will practice
3-64. Use the Distributive Property to find each product below.
1.
6(−3x + 2)
2.
x2(4x − 2y)
3.
5t(10 − 3t)
4.
−4w(8 − 6k2 + y)
3-65. Write the area as a product and as a sum for the rectangle shown at
right.
3-66. Now examine the following diagram. How is it similar to the set
of tiles in problem 3-65? How is it different?
3-67. Diagrams like the one in problem 3-66 are referred to as generic rectangles. Generic rectangles
(Punnette Squares) allow you to use an area model to multiply expressions without using the algebra tiles.
Find the area of each part and write the area of the whole rectangle as a product and as a sum.
3-68. Multiply and simplify the following expressions using both a Punnette
Square (generic rectangle) and using the FOIL method.
a)
(x + 5)(3x + 2)
b)
(2y − 5)(5y + 7)
c)
3x(6x2− 11y)
d)
(5w − 2p)(3w + p − 4)
3-69. THE GENERIC RECTANGLE CHALLENGE
Fill in the missing dimensions and areas. Then write the entire area as a product and as a sum.
a.
b.
c.
d,
Review these Properties of Real Numbers
Be prepared for a quiz!
The legal tiles moves have formal mathematical names, called the properties of real numbers.
The Commutative Property states that when adding or multiplying two or more numbers or terms, order is not
important. That is:
a+b=b+a
a·b=b·a
For example, 2 + 7 = 7 + 2
For example, 3 · 5 = 5 · 3
However, subtraction and division are not commutative, as shown below.
7 − 2 ≠ 2 − 7 since 5 ≠ −5
50 ÷ 10 ≠ 10 ÷ 50 since 5 ≠ 0.2
The Associative Property states that when adding or multiplying three or more numbers or terms together,
grouping is not important. That is:
(a + b) + c = a + (b + c) For example, (5 + 2) + 6 = 5 + (2 + 6)
(a · b) · c = a ·(b · c)
For example, (5 · 2) · 6 = 5 · (2 · 6)
However, subtraction and division are not associative, as shown below.
(5 − 2) − 3 ≠ 5 −(2 − 3) since 0 ≠ 6
(20 ÷ 4) ÷ 2 ≠ 20 ÷(4 ÷ 2) since 2.5 ≠ 10
The Identity Property of Addition states that adding zero to any expression gives the same expression. That
is:
a+0=a
For example, 6 + 0 = 6
The Identity Property of Multiplication states that multiplying any expression by one gives the same
expression. That is:
1·a=a
For example, 1 · 6 = 6
The Additive Inverse Property states that for every number a there is a number –a such that a +( −a) = 0. A
common name used for the additive inverse is the opposite. That is, –a is the opposite of a. For example, 3
+ (−3) = 0 and −5 + 5 = 0
The Multiplicative Inverse Property states that for every nonzero number a there is a number
A common name used for the multiplicative inverse is the reciprocal. That is,
of a. For example,
HW 21 3-70 – 3-75
.
such that
is the reciprocal