Question

[Fin3]

Answer 1

[Kiều Vũ Linh]

29) 2.x⁴ = 2.3⁴

x⁴ = 3⁴

x = 3 hoặc x = -3

30) 5.x³ = 5.4³

x³ = 4³

x = 4

31) 7/5 . x⁵ = 7/5 . 4⁵

x⁵ = 4⁵

x = 4

32) 3/4 . x¹² = 3/4 . 5¹²

x¹² = 5¹²

x = 5 hoặc x = -5

33) 9.x⁶ = 9.7⁶

x⁶ = 7⁶

x = 7 hoặc x = -7

34) x⁹ = 2.2⁸

x⁹ = 2⁹

x = 2

35) x¹² = 5⁴.5⁸

x¹² = 5¹²

x = 5 hoặc x = -5

36) 5.3ˣ = 7.3⁵ - 2.3⁵

5.3ˣ = 3⁵.(7 - 2)

5.3ˣ = 5.3⁵

3ˣ = 3⁵

x = 5

37) 9.x⁶ = 6.5⁶ + 3.5⁶

9.x⁶ = (6 + 3).5⁶

9.x⁶ = 9.5⁶

x⁶ = 5⁶

x = 5 hoặc x = -5

38) x¹⁰ = 4.4¹⁰ - 3.4¹⁰

x¹⁰ = (4 - 3).4¹⁰

x¹⁰ = 4¹⁰

x = 4 hoặc x = -4

Answer 2

[Kiều Vũ Linh]

39) 7.x⁷ = 5.3⁷ + 2.3⁷

7.x⁷ = (5 + 2).3⁷

= 7.x⁷ = 7.3⁷

x⁷ = 3⁷

x = 3

40) 7.x⁸ = 2⁹ + 5.2⁸

7.x⁸ = (2 + 5).2⁸

7.x⁸ = 7.2⁸

x⁸ = 2⁸

x = 2 hoặc x = -2

41) 5.x¹⁰ = 8.3¹⁰ - 3.3¹⁰

5.x¹⁰ = (8 - 3).3¹⁰

5.x¹⁰ = 5.3¹⁰

x¹⁰ = 3¹⁰

x = 3 hoặc x = -3

42) 5.(x + 6)⁵ = 2.3⁵ + 3.3⁵

5.(x + 6)⁵ = (2 + 3).3⁵

5.(x + 6)⁵ = 5.3⁵

(x + 6)⁵ = 3⁵

x + 6 = 3

x = 3 - 6

x = -3

43) (2x + 1)⁸ = 5.9⁷ + 4.9⁷

(2x + 1)⁸ = (5 + 4).9⁷

(2x + 1)⁸ = 9.9⁷

(2x + 1)⁸ = 9⁸

2x + 1 = 9 hoặc 2x + 1 = -9

*) 2x + 1 = 9

2x = 8

x = 4

*) 2x + 1 = -9

2x = -10

x = -5

Vậy x = -5; x = 4

44) (x + 1)³ + 4.(x + 1)³ = 5.3⁶

5(x + 1)³ = 5.(3²)³

(x + 1)³ = 9³

x + 1 = 9

x = 8

45) 1/5 . (x + 2)² + 1/3 . (2x - 2)³ = 1/5 . (x + 2)² + 1/3 . 2³

1/3 . (2x  - 2)³ = 1/3 . 2³

(2x - 2)³ = 2³

2x - 2 = 2

2x = 4

x = 2

46) 2/3 . (2x + 4)² - 1/3 . (x + 1)² = -1/3 . (2x + 4)² + 2/3 (x + 1)²

2/3 (2x + 4)² + 1/3 (2x + 4)² - 1/3 (x + 1)² - 2/3 (x + 1)² = 0

(2x + 4)² - (x + 1)² = 0

(2x + 4)² = (x + 1)²

2x + 4 = x + 1 hoặc 2x + 4 = -x - 1

*) 2x + 4 = x + 1

2x - x = 1 - 4

x = -3

*) 2x + 4 = -x - 1

2x + x = -1 - 4

3x = -5

x = -5/3

Vậy x = -3; x = -5/3