 # Roots and powers Chapter 4.

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Roots and powers Chapter 4

4.1 – Estimating roots Chapter 4

Pg. 206, #1–6 Independent Practice

4.2 – irrational numbers Chapter 4

Rational and irrational numbers

Irrational numbers An irrational number cannot be written in the form m/n, where m and n are integers and n ≠ 0. The decimal representation of an irrational number neither terminates nor repeats. When an irrational number is written as a radical, the radical is the exact value of the irrational number. approximate values exact value

example Tell whether each number is rational or irrational. Explain how you know. a) b) c) –3/5 is rational, because it’s written as a fraction.  In its decimal form it’s –0.6, which terminates. b) is irrational since 14 is not a perfect square. The decimal form is … which neither repeats nor terminates. c) is rational because both 8 and are perfect cubes. Its decimal form is … which is a repeating decimal.

The number system Together, the rational numbers and irrational numbers for the set of real numbers. Real numbers Rational numbers Integers Irrational numbers Whole numbers Natural Numbers

example Use a number line to order these numbers from least to greatest.

Pg , #4, 7, 8, 12, 15, 18, 2o Independent Practice

4.3 – Mixed and entire radicals
Chapter 4

Draw the following triangles on the graph paper that has been distributed, and label the sides of the hypotenuses. 1 cm 4 cm 1 cm 3 cm 3 cm 2 cm 4 cm Draw a 5 by 5 triangle. What are the two ways to write the length of the hypotenuse? 2 cm

Why? We can split a square root into its factors. The same rule applies to cube roots. Why?

where n is a natural number, and a and b are real numbers. We can use this rule to simplify radicals:

example Simplify each radical. a) b) c)

example Write each radical in simplest form, if possible. a) b) c)
Try simplifying these three:

example Write each mixed radical as an entire radical. a) b) c)
Try it:

P , #4, 5, 10 and 11(a,c,e,g,i), 14, 19, 24 Independent practice

4.4 – fractional exponents and radicals
Chapter 4

Fill out the chart using your calculator.
Fractional exponents Fill out the chart using your calculator. What do you think it means when a power has an exponent of ½? What do you think it means when a power has an exponent of 1/3? Recall the exponent law: When n is a natural number and x is a rational number:

example Evaluate each power without using a calculator. a) b) c) d)
Try it:

Powers with rational exponents
When m and n are natural numbers, and x is a rational number, Write in radical form in 2 ways. Write and in exponent form.

example Evaluate: a) b) c) d)

example Biologists use the formula b = 0.01m2/3 to estimate the brain mass, b kilograms, of a mammal with body mass m kilograms. Estimate the brain mass of each animal. A husky with a body mass of 27 kg. A polar bear with a body mass of 200 kg.

Pg , #3, 5, 10, 11, 12, 17, 20. Independent practice

4.5 – negative exponents and reciprocals
Chapter 4

challenge Factor: 5x2 + 41x – 36

Hint: try using fractions.
consider This rectangle has an area of 1 square foot. List 5 possible pairs of lengths and widths for this rectangle. (Remember, they will need to have a product of 1). Hint: try using fractions.

What is the rule for any number to the power of 0? Ex: 70?
reciprocals Two numbers with a product of 1 are reciprocals. So, what is the reciprocal of ? So, 4 and ¼ are reciprocals! What is the rule for any number to the power of 0? Ex: 70? If we have two powers with the same base, and their exponents add up to 0, then they must be reciprocals. Ex: 73 ・ 7-3 = 70

So, 73 and 7-3 are reciprocals.
73 ・ 7-3 = 70 So, 73 and 7-3 are reciprocals. What is the reciprocal of 343? 73 = 343 When x is any non-zero number and n is a rational number, x-n is the reciprocal of xn. That is,

example Evaluate each power. a) b) c) Try it:

example Evaluate each power without using a calculator. a) b) Recall:
Try it (without a calculator):

example Paleontologists use measurements from fossilized dinosaur tracks and the formula to estimate the speed at which the dinosaur travelled. In the formula, v is the speed in metres per second, s is the distance between successive footprints of the same foot, and f is the foot length in metres. Use the measurements in the diagram to estimate the speed of the dinosaur.

Pg , #3, 6, 7, 9, 13, 14, 16, 21 Independent Practice

4.6 – applying the exponent laws
Chapter 4

Exponent laws review Recall:

Try it Find the value of this expression where a = –3 and b = 2.

example Simplify by writing as a single power. a) b) c) d) Try these:

example Simplify. a) b) Try this:

example Simplify. a) b) c) d) Try these:

example A sphere has volume 425 m3.
What is the radius of the sphere to the nearest tenth of a metre?

Pg , #9, 10, 11, 12, 16, 19, 21, 22 Independent Practice