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Learn about exponents, square roots, and perfect squares, and how they are applied to simplify expressions and solve problems. Complete the homework assignment for practice.
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Bell Work: In the expression 4ac, what is the constant?
Answer: 4
Exponent*: Indicates how many times the base number is to be used as a factor. In the expression 5 , 5 is the base and 2 is the exponent. 2
3 In the expression 5 , we could also write it as 5 x 5 x 5 = 125. We read 5 as “five squared” and 5 as “five cubed.” We say “to the nth power” if the exponent n is greater than 3. For example, 5 is read as “five to the fourth power” or just “five to the fourth.” 2 3 4
Example: Simplify 5 10 4 4
Answer: 5 x 5 x 5 x 5 = 625 10 x 10 x 10 x 10 = 10,000 Notice that the number of zeros in 10,000 matches the exponent of 10.
Example: Write the prime factorization of 72 using exponents.
Answer: 72 = 2 x 2 x 2 x 3 x 3 72 = 2 x 3 3 2
We can use exponents with units of length to indicate units of area. The formula for the area of a square is A = s . In this formula, A represents area and s represents the length of the side. 2
Example: The figure shows a square floor tile that is one foot on each side. Find the are covered by the tile in square inches using the area formula. 12 inches
Answer: A = 12 = 144 inches 2 2
Exponents can be applied to variables. If the same variable is a factor in an expression a number of times, we can simplify the expression by writing the variable with an exponent.
Example: Express with exponents. 2xxyyyz
Answer: 2x y z 2 3
Radical Expression*: an expression that indicates the root of a number. Radicand*: The number under a radical sign. Index*: Indicates a root of a number.
The inverse of raising a number to a power is taking a root of a number. We may use a radical sign, √ , to indicate a root of a number. √25 = 5 √125 = 5 3
If the index is 4 or more, we say “the nth root.” √9 = square root of 9 √27 = cubed root of 27 √125 = the fourth root of 125 3 4
Example: Simplify √144 √27 3
Answer: 12 x 12 = 144 = 12 3 x 3 x 3 = 27 = 3
A number that is a square of a counting number is a perfect square. For example, 25 is a perfect square because 5 = 25. The number 64 is both a perfect square and a perfect cube. 2
Answer: 8 x 8 = 64 and 4 x 4 x 4 = 64 √64 > √64 3
Practice: The floor of a square room is covered with square foot tiles. If 100 tiles cover the floor, how long is each side of the room?
Answer: √100 = 10 feet
Practice: Name the first three counting numbers that are perfect squares. Then find their positive square roots.
Answer: (1 x 1) = 1 (2 x 2) = 4 (3 x 3) = 9 √1 = 1 √4 = 2 √9 = 3
HW: Lesson 15 #1-30 Due Next Time