Question

Tìm x biết :

a) 2² + 4x = 43

b) 2ⁿ⁺²+ 4 = 36

c) 5 + (4 + x3) = 45

Answer 1

a) 2² + 4x = 43

4 + 4x = 43

4x = 43 - 4

4x = 39

x = 39 : 4

x = 9,75.

b) 2^{n + 2} + 4 = 36

\(\Rightarrow\) 2ⁿ . 2² + 2² . 1 = 36

\(\Rightarrow\) 2² . (2ⁿ + 1) = 36

4 . (2ⁿ + 1) = 36

2ⁿ + 1 = 36 : 4

2ⁿ + 1 = 9

2ⁿ = 9 - 1

2ⁿ = 8

\(\Rightarrow\) 2ⁿ = 2³

\(\Rightarrow\) n = 3.

c) 5 + (4 + x3) = 45

4 + x3 = 45 - 5

4 + x3 = 40

x3 = 40 - 4

x3 = 36

x = 36 : 3

x = 12.

Answer 2

a) 2² + 4x = 43

=> 4 + 4x = 43

=> 4x = 43 - 4

=> 4x = 39

=> x = 39 : 4

=> x = \(\dfrac{39}{4}\)

Vậy x = \(\dfrac{39}{4}\)