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D. RADICAL EQUATIONS

Definition

An equation that has a variable in a radicand is called a radical equation.

For example, the equations ñx = 25, x 1 3, and 2x – 1 3x 5 are radical equations. Let us look at some examples of how to solve radical equations.

EXAMPLE 19 Solve x 1 3.

Solution ( x 1)2 32 (take the square of both sides) x 1 9

x 8

 

20 Solve

3x 1 5.

EXAMPLE

 

 

 

Solution (

3x 1)2 52

 

 

3x 1 25

 

 

 

3x 24

 

 

 

x 8

 

21 Solve

2x 3 3 8.

EXAMPLE

 

 

 

Solution

2x 3 3

8

 

 

 

2x 3

8 – 3

 

 

 

2x 3

5

 

(

2x 3)2 52

 

 

 

2x 3 25

 

 

 

2x 22

 

 

 

x 11

?

Check: 8 1 3

?

9 3

3 3 Therefore, 8 is a solution.

?

Check: 3 8 1 5

?

25 5

5 5 Therefore, 8 is a solution.

Check:

?

2 11 3 3 8

?

25 3 8

?

5 3 8

8 8 Therefore, 11 is a solution.

Radical Functions

99

EXAMPLE 22 Solve x2 12 x 6.

Solution ( x2 12)2 (x 6)2

x2 12 x2 12x 36 12x –24

x –2

EXAMPLE 23 Solve 3 3x 2 5.

Solution (3 3x 2)3 53

3x 2 125

3x 123 x 41

 

24 Solve 4x 1 –

5x – 1 0.

EXAMPLE

 

 

Solution 4x 1 – 5x – 1

0

 

( 4x 1)2

( 5x – 1)2

4x 1 5x – 1 x 2

?

Check: (–2)2 12 – 2 6

?

4 12 4

?

16 4

4 4

Therefore, –2 is a solution.

?

Check: 3 3 41 2 5

?

3 123 2 5

?

3 125 5

5 5

Therefore, 41 is a solution.

Check:

4 2 – 1 –

?

5 2 – 1 0

?

9 – 9 0

?

3 – 3 0

0 0

Therefore, 2 is a solution.

100

Algebra 11

 

25 Solve 3x 1

3x 6 5.

 

 

EXAMPLE

 

 

 

 

 

 

 

 

Solution

3x 1

5 –

3x 6

 

 

 

(

3x 1)2

(5 –

3x 6)2 (take the square of both sides)

 

 

3x 1

25 – 2 5

3x 6

3x 6

(simplify)

 

10

3x 6

30

 

 

 

 

 

(

3x 6)2

32

 

 

 

 

 

 

 

3x 6

9

 

 

 

 

 

3x 3

 

 

x 1

 

 

Check: 3 1 1 –

3 1

?

6 5

 

4

?

 

9 5

?

2 3 5

5 5

Therefore, 1 is a solution.

Check Yourself 5

Solve each equation and check your answer.

a. ñx = 5

b. ñx + 1 = 3

d. ñx = –3

e.

2x – 1 7

g.

3x – 5 4 6

h.

5x 1 – 3 0

 

 

 

2

j.

4x – 3 – 2x – 2 0

k.

x 3 x – 2 5

l.

x2 1 2 – x

m. 3 x 1 3

o. 3 3x 2 3 5x

p. 4 x 4 2x – 1

c.óx+1 = 6

f. 3 x 1 – 1 8

i.

2x 6 – x

n. 3 x 2

Radical Functions

101

EXERCISES 2.1

A.Radical Expressions

1.Evaluate the expressions.

a.

4

16

b.

4 16

c.

4 16

d.

3

27

e.

25

f.

25 3

 

 

8

 

4

 

 

g.

3

27 2

h.

4 0.0625

i.

7 128

2.Write each expression in its simplest form. All the variables represent positive real numbers.

a. 4x4 y12

b.

3 25a6 y12

c.

4 64x4 y20

d.

5 32x15 y20

e.

5 4 xy

f.

3 3

3 x2 y3

g.

4 x16

h. 3 9a2 3 9a

i.

4 x 3 y5

j.

12 243x6 y12

 

 

xy

 

 

 

 

k. 16 312(x+ y)12

l.

4 3

(x a)20(a x)28

3. Write each expression in its simplest form. All the variables represent positive real numbers.

a. 3 x2 6 x5

b.

x5

4 x3

 

 

x 3 x2

c.

(x2

xy 3 y2 )2 4 x3

d. 4 58 x 4 34 x5 + 4 252 x9

e. 4 2x 4 x3 4 4x2

2xy 2x 2y

4.Write each expression in its simplest form.

a.3 16 3 54 + 3 128

b.4 32 + 4 162 4 512

c.4 162 3 54 + 4 32 + 3 16

5. Rationalize the denominator of each fraction.

a.

1

 

 

 

b.

 

x

c.

5 2

 

 

 

 

 

 

 

 

 

 

3 2

 

 

3 5

 

 

 

4

x

 

 

d.

 

4

 

 

e.

 

 

1

 

 

f.

12 x11 1

 

 

3 2 1

 

3

x +1

 

3 x

g.

1

 

 

h.

 

1

 

 

i.

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3 3 3 2

4 2 1

3 16 3 12 + 3 9

j.

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(16 3 +1)(

8 3 +1)( 4 3 +1)(

3 +1)

 

 

 

 

 

6.Evaluate each expression.

a.56+ 56+ 56+...

b.6 32 6 32 6 32 ...

c.4 32 4 32 4 32 ...

102

Algebra 11

7. Prove each equality.

a.

n a n a n a ... = n 1 a

b.

n a n a n a ... = n 1 a

c.

n a m a n a m a ... = mn 1 am 1

d.

a+ a+ a+... =

4a+1+1

 

 

 

2

 

B.Rational Exponents

8.Evaluate each expression.

a.

91/2

b.

–91/2

c.

(–9)1/2

d.

–81/3

e.

(–8)1/3

f.

01/16

g.

163/4

h.

324/5

 

 

9. For each statement, give a possible value for a.

a.

(a2)1/2 a

b.

(a2)1/2

= a

c.

(a2)2 = a

d.

(a1/2)2

a

e. (a1/2)2 = a

10.Evaluate the expressions.

a. (–8)7/3 91/2

b. 641/3 + 31/2 9 3–5/2

c. 41.5 ( 91) 0.5 ( 641 ) 2 / 3 ( 45)3.5 0.83.5

11.Simplify the expressions. All the variables represent positive real numbers.

a. (2x1/2) (3x1/3)

b. x2/5 251/2 x3/5

 

c.

4x5 / 2 1/ 2

d.

1/2

1/2

1/2

1/2

( x2 / 5 )

(x y )(x + y )

e.

361/ 2 x1/ 4

f.

 

–1/2

y

2/5

3

 

641/ 2 x3 / 5

(2x

 

 

)

 

12.Write each expression as a radical expression. All the variables represent positive real numbers.

a.

a3/5

b.

x–1/3

c.

a–4/5

d.

x–1/2y1/2

e.

(x1/2)1/3

f.

x–2/7

g.

y–5/3

h.

5a3/2

i.

(x2y3)1/2

j.

(4ab2)5/7

k.

(7x3y)–1/3

l.

(a + b)3/2

13.Write each expression as an expression with a rational exponent. All the variables represent positive real numbers.

a.

3 x

b.

4 a

c.

x2 + y2

d. 5 (3a)2

e.

3 (x y) 1

f.

6 x12 y12

g. ña + ñb

h. 34 a3

i.

5x5 y2

j.

7 (x2 y3 )3

k.

9 (x 3y)2

l.

3 a + 5 x+ y2

Radical Functions

103

14.Simplify each expression by converting the radicals into rational powers.

a.

4 a2

3 a

 

 

 

 

a

 

b.

c4 / 5 3 a 2

(8a 2c) 1/ 3

5

c 1

 

 

15.Simplify each expression.

a.(x1/2 + 2y1/2)(x1/2 – 3y1/2)

b.(3a1/2 b1/2)(a1/2 – 2b1/2)

c.2x1/3(3x2/3 x8/3)

d.3a4/5(2a1/5 a6/5)

e.(3x1/2 – 2y1/2)(3x1/2 + 2y1/2)

f.(3x1/2 + y1/2)2

16. Simplify each expression.

a.

a2 / 5

b2 / 5

 

 

 

 

 

 

 

a1/ 5

b1/ 5

 

 

 

 

 

 

b.

 

a3 / 4 +b3

/ 4

 

 

 

a1/ 2

a1/ 4 b1/ 4

+ b1/ 2

 

c.

x+ y1/ 2

 

x4 / 3

y2 / 3

1/ 3 1/ 6

 

 

 

 

 

 

1/ 3 + x y

1/ 3

1/ 6

 

2 / 3

 

 

x

+ y

 

x

+ y

 

d.

c 27

 

3c1/ 3 +18

 

 

 

c2 / 3 9

 

c1/ 3 +3

 

C.Exponential Equations

17.Solve the equations.

a.32x = 81

b.7x = 72 – x

c.25x = 53 – x

d.3x2 – 5x +8 = 9

18.(23)x = 4 1.5 is given. Find x.

19.Find the real number y which satisfies

x= 22y+4 and x3 = 210y+4.

20.Find the real numbers x and y which satisfy 0.0064y 1000x = 45.

21.Find the real number x which satisfies

(–4x + 1)2n = (x2 + 2x + 1)n, n .

22.Find the possible values of a which satisfy 2a+1 + 4a = 80.

23.Find the real number x which satisfies

xm 15 + xm 16 + xm 17

xm 18 + xm 17 + xm 16 =128.

104

Algebra 11

D.Radical Equations

24.Write the expressions in exponential form and simplify if possible.

a.

ò21

b.

72

c.

7 5

d. 3 a2 x3

e.

3 5 2

f.

( 5 3)6

g.

3 1

 

 

 

 

 

 

3

 

25. Write the expressions in radical form.

 

1

 

2

 

 

3

3

 

ab

 

 

3

 

1

a.

a2

b. b

c.

(

d.

x c

e.

(a

)

3

2)

 

2

2

6

 

 

 

 

 

 

 

 

 

 

26. Simplify the expressions.

 

 

a.

 

3 3

b.

4

5 a2

c.

1016

d.

3

5

5

e.

5 243

f.

(–5)4

g.

3

–27

h. 3 64x6

i.

a3 3 a2

j.

3

2 3 4

k.

4

3 4 27

l.

162

 

 

 

 

 

 

 

 

2

m.

 

3

2

n.

4

3 21

o.

3

3 250

6

7

3 5

p.

3 34 9 3

q. 4 23 3 24 25

 

 

27. Perform the operations.

a.

 

3 3 2

b.

2 3 3 6 6

 

 

 

 

6 108

 

 

 

 

 

 

c.

3

11– 3 4 – 3 27

d.

7

3

2

 

10

 

 

2 9

 

27

e. 4 17 6 8

f.

( 2 – 6)( 2 3 )

28. Solve the equations.

a.

2x 1 3

b.

3x – 14 8

c. ò7x = x

d.

3 4x 6

e. 3 5x – 4 6

f.

3 7x 6 5

g.

5x – 1 3 7

h.

2x – 3 – 2 4

i.

x2 5 x 1

j.

x2 9 5

k. 3 7x – 6 4

l.

2x – 5 x – 4

m. x

x 16 – 2

n.

6

 

2

 

 

 

 

 

x

3

 

o. ñ6x x= 5

 

 

 

 

 

p.

x 1 2 x x 1– 2 x 8

 

 

q.33x – 6 1

92x 1 93

r.

4 3 8x – 2

6

 

1

 

 

4x – 3

 

 

 

 

 

s.

1

 

1

 

 

2

 

 

 

 

 

 

2 – x

2

x

Radical Functions

105

Mixed Problems

29. Evaluate

a 3 / 2 b(ab–2 )–1/ 2

(a–1 )–2 / 3

3

if a =

2

and b =

1

.

 

 

 

 

 

2

 

3 2

 

 

 

 

 

 

30. Evaluate

4 8

2 1

4 8

2 1 .



 

4 8

2 1

 

31. Order the numbers 16 64, 10 74 7 and 4 2

5 .



4

 

32. Find the sum of all values of x which satisfy (x – 3)x2 – 6x + 5 = 1.

33. Find the possible values of x which satisfy



x 25 x 25 x 25 ... = 25.

34. Solve the equation (7 3 5x 6 )+90 = 3 5x .



35. Solve the equation

3

 

x 3

 

10

7 = 0, x .

 

5

 

+ 3 5x 3



 

 

36. Solve the equation x 2 2x = 4.

37. Solve the equation



3

5 + 3+ 5 =10 x+2 2 x+1.

106

Algebra 11

CHAPTER REVIEW TEST 2A

1. Evaluate 43 82

163.

 

 

A) 212

B) 224

C) 424

D) 812

E) 168

2. Solve 9x+2 = 243 for x.

 

 

 

A)

1

B)

1

C) 1

D) 2

E) 3

 

3

 

2

 

 

 

3. Simplify 2k 7k (–2)k if k is an odd integer.

A) 14k B) 27k C) 7k D) 7k E) (–7)k

4.a = (84)7, b = (45)8 and c = 2(34) are given. Which one of the following is correct?

A) a < b < c

B) c < b < a

C) c < a < b

D) b < c < a

 

E) b < a < c

5. Evaluate 810.25 + 490.5 + 320.2.

 

 

A) 10

B) 12

C) 14

D) 16

E) 20

6. Simplify 23a b 22b a + 2a b 2a + 2b.

A) 22b+a+1

B) 2b – 2a

C) 22a+b+1

D) 22a b

 

E) 22a+2

7.

Simplify

(2x+1 )3

 

(2

x+2 2 .

 

 

 

)

 

 

A) 2x – 1

 

B) 2x+1

C) 22x+1

 

 

D) 2x – 2

E) 22x+2

8. Simplify

23t +23t +23t +23t +23t +23t +23t +23t .

 

 

 

8t+1

 

A) 0

B) 1

C) 2

D) 2t

E) 2t+1

Chapter Review Test 2A

107

9. Evaluate 100–3 58

45.

A) 200 B) 400

C) 50 D) 100 E) 250

10. Evaluate

4+

23+ 4 .

 

 

A) 3

B) 4

C) 5

D) 6

E) 8

11. Evaluate

0.64 +

0.09 2

2.25.

A) –2.4

B) –2.2

C) –1.9

D) –1.1 E) –0.9

12. Simplify

18k5

72k3 .

 

A) 6k4

B) 36k4

C) ñ6k D) k3

E) 36k

13. Evaluate

3

+

2+

1 .

 

 

 

 

 

8

 

 

4

 

 

 

A)

3

 

 

 

B)

3

 

C) ò18

2

 

 

 

2

 

 

 

 

 

 

 

 

 

D)

5

 

 

 

 

E)

15

 

4

 

 

 

 

8

 

 

 

 

 

 

 

14. Evaluate 5 3 0.008.

A) 3 0.04 B) 3 0.2 C) 0.01 D) 0.1 E) 1

15. Evaluate

 

2 +2

6

.

 

 

2

2 –

6

 

 

A)

12 6

 

 

 

B) 12

C) 2ñ6 – 2

 

5

 

 

 

 

 

 

D) 8 + 5ñ3

 

 

E) 2 + 2ñ6

16. Order 5ñ2, 4ñ3 and 7.

 

A) 4ñ3 < 5ñ2 < 7

B) 5ñ2 < 7 < 4ñ3

C) 7 < 4ñ3 < 5ñ2

D) 4ñ3 < 7 < 5ñ2

E) 7 < 5ñ2 < 4ñ3

108

Algebra 11