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Find the two square roots of each number.
Exploring Square Roots and Irrational NumbersExploring Square Roots and Irrational NumbersCOURSE 3 LESSON 4-8COURSE 3 LESSON 4-8
a. 81
9 • 9 = 81
–9 • (–9) = 81
The two square roots of 81 are 9 and –9.
b. 1
36
16
16– –• =
136
The two square roots of
are and – .16
16
136
16
16• =
136
4-8
Estimate the value of – 70 to the nearest integer.
Exploring Square Roots and Irrational NumbersExploring Square Roots and Irrational NumbersCOURSE 3 LESSON 4-8COURSE 3 LESSON 4-8
Since 70 is closer to 64 than it is to 81, – 70 –8.
4-8
The math class drops a small ball from the top of a stairwell.
They measure the distance to the basement as 48 feet. Use the
formula d = 16t2 to find how long it takes the ball to fall.
Exploring Square Roots and Irrational NumbersExploring Square Roots and Irrational NumbersCOURSE 3 LESSON 4-8COURSE 3 LESSON 4-8
48 = 16t2 Substitute 48 for d.
d = 16t2 Use the formula.
= t2 Divide each side by 16.4816
3 = t2 Simplify.
4-8
(continued)
Exploring Square Roots and Irrational NumbersExploring Square Roots and Irrational NumbersCOURSE 3 LESSON 4-8COURSE 3 LESSON 4-8
It takes about 1.7 seconds for the ball to fall 48 ft.
3 = t Find the positive square root.
Use a calculator.3 1.7320508
Round to the nearest tenth.1.7 t
4-8
Identify each number as rational or irrational. Explain.
Exploring Square Roots and Irrational NumbersExploring Square Roots and Irrational NumbersCOURSE 3 LESSON 4-8COURSE 3 LESSON 4-8
d. 6.36366366636666. . . Irrational; the decimal does not terminate or repeat.
Rational; the decimal repeats.a. –9.3333
b. 479 Rational; the number can be written as the ratio .
439
Irrational; 90 is not a perfect square.c. 90
4-8
1. Find the two square roots of 400.
2. Estimate 34 to the nearest integer.
3. Using d = 16t 2, find how long it takes a skydiver to fall 676 ft from
an airplane.
4. Is rational or irrational? Explain.
Exploring Square Roots and Irrational NumbersExploring Square Roots and Irrational Numbers
20 and –20
6
COURSE 3 LESSON 4-8COURSE 3 LESSON 4-8
6.5 s
Rational; it can be written as .85
64 5
4-8
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