Exponents and Scientific Notation

Lesson 5

Math

Unit 1

8th Grade

Lesson 5 of 15

Objective


Apply the product of powers rule and the quotient of powers rule to write equivalent, simplified exponential expressions.

Common Core Standards


Core Standards

  • 8.EE.A.1 — Know and apply the properties of integer exponents to generate equivalent numerical expressions. For example, 3² × 3-5 = 3-3 = 1/3³ = 1/27.

Criteria for Success


  1. Investigate, determine, and apply the general rule for product of powers: $${x^mx^n=x^{m+n}}$$.
  2. Investigate, determine, and apply the general rule for quotient of powers: $${{x^m\over{x^n}}=x^{m-n}}$$

Tips for Teachers


  • These Anchor Problems can be used in a variety of ways, but one effective approach is to have students lead the work rather than the teacher. Similar to the previous lesson, students can investigate and explore these problems, but now with the added objective of determining an approach to solving problems in general. 
  • Once students have experimented with the problems and found a generalization, then provide them with the name of the rule and the general form. 
  • Throughout the next few lessons, the problems will become increasingly complex as new rules are learned and named. It is important for students to be able to look at an exponential expression and see the structure in the problem that can help them understand what to do (MP.7). This is more important and will be more useful to students than memorizing the rules. You may consider having students create posters or other visual displays that they can refer to throughout the unit.
  • Note that negative exponents are not included in this lesson, as they will be introduced in Lesson 8.
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Anchor Problems

25-30 minutes


Problem 1

Write an equivalent, simplified form of each of the following:

a.   $${6^3\times6^5}$$

b.   $${\left (-{1\over4} \right )^4\left (-{1\over4} \right )^3}$$

c.   $${12^a\cdot 12^b}$$

d.   $${x^mx^n}$$

Guiding Questions

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Student Response

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Problem 2

Write an equivalent, simplified form of each of the following:

a.   $${5^3\cdot 25\cdot 5^4}$$

b.   $${5^63^2\times3\times5^3}$$

c.   $${(2xy)(x^2y^3)(2y^4)}$$

Guiding Questions

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Student Response

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Problem 3

Write an equivalent, simplified form of each of the following:

a.    $${8^6\over8^3}$$

b.    $${{\left (-{1\over2} \right )^9}\over{\left (-{1\over2} \right )^5}}$$

c.    $${\frac{6^{4}5^{7}}{6\cdot 2^{5}}}$$

d.    $${x^m\over x^n}$$, where ($$m > n$$)

Guiding Questions

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Student Response

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Problem 4

Your teacher writes the following two expressions on the board:

Your teacher asks the class if these two expressions are equivalent. Half of the class says yes, and half says no. What do you think? Convince the other half of the class that you are correct.

Guiding Questions

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Student Response

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References

Nathan Kraft's Blog Exponent Rules are Lame

Exponent Rules are Lame is made available on Nathan Kraft's Blog. Accessed Aug. 4, 2017, 10:11 a.m..

Problem Set

15-20 minutes


Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.

Target Task

5-10 minutes


Simplify the following expressions.

a.   $$17^x(17^y)$$

b.   $$2^4(32)$$

c.   $$5^a\over 5^b$$

d.   $$3^6÷27$$

Student Response

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Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

  • Include problems where students are given an exponential expression and must write a more complex, equivalent expression (for example, write an expression equivalent to $${3^{2+4},x^{5-2},y^8}$$).

Next

Apply the power of powers rule and power of product rule to write equivalent, simplified exponential expressions.

Lesson 6
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Review of Exponents

Topic B: Properties of Exponents

Topic C: Scientific Notation

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