Question

sos giúp mik vs ạ

Answer 1

10) (x + 3/4) - 5 = -2

x + 3/4 = -2 + 5

x + 3/4 = 3

x = 3 : 3/4

x = 4

11) 3,8 : 2x = 1/4 : 2 2/3

3,8 : 2x = 1/4 : 8/3

3,8 : 2x = 3/32

2x = 3,8 : 3/32

2x = 608/15

x = 608/15 : 2

x = 304/15

12) (2x + 1)(x - 1/7) = 0

2x + 1 = 0 hoặc x - 1/7 = 0

*) 2x + 1 = 0

2x = -1

x = -1/2

*) x - 1/7 = 0

x = 1/7

Vậy x = -1/2; x = 1/7

13) 7²ˣ + 7²ˣ⁺² = 2450

7²ˣ.(1 + 7²⁾ = 2450

7²ˣ.50 = 2450

7²ˣ = 2450 : 50

7²ˣ = 49

49ˣ = 49

x = 1

14) 81/625 = (3/5)ˣ

(3/5)⁴ = (3/5)ˣ

x = 4

15) 7(x - 1) + 2x(1 - x) = 0

7(x - 1) - 2x(x - 1) = 0

(x - 1)(7 - 2x) = 0

x - 1 = 0 hoặc 7 - 2x = 0

*) x - 1 = 0

x = 1

*) 7 - 2x = 0

2x = 7

x = 7/2

Vậy x = 1; x = 7/2