Download 2.5 Algebra 1 Section 2.5

Algebra 1 Section 2.5
Multiply real numbers
Recall: 4 x (-3) means
(-3)+(-3)+(-3)+(-3)
= -12
Also (-4)(-3) = 12
because – (-12) = 12
Rules for multiplying real numbers
1. The product of two numbers with the
same sign is positive.
2. The product of two numbers with
opposite signs is negative.
Simplify
(-8)(-5)
(-⅔)(-9)
(6)(-4)
(-4)(-3)(2)(-5)
(-11)(3)
If there are an odd number of negative
factors, the product is negative.
• Simplify
(-3)(-x)
5(-n)(-n)(-n)
(-1)(-a)2
- (-2)5
Evaluate -8x if x = -3
3x2 – 5x if x = -4
-2 | x – 5 | if x = -5
Use a calculator.
(-18.7)(4.6)(-3.6)
Properties of multiplication
Commutative property
axb= bxa
Associative property (a x b) x c = a x (b x c)
Identity property
a (1) = a
Identify the property shown.
5(3x7) = (5x3)x7
1 (4) = 4
5(7) = (7)5
Page 95 example 4
assignment
Page 96
Problems 16 – 56 even, 61,62,63