Question

1. Tìm x, biết :

a) 27^x : 3^x = 9

b) 25 : 5^x = 5

c) 2 : (x + 2)² = \(\dfrac{1}{18}\)

d) (5x - 1)² = \(\dfrac{36}{49}\)

e) \(\left(\dfrac{3}{4}\right)^x=\dfrac{2^8}{3^4}\)

g) \(\left(\dfrac{-2}{5}\right)^x=\dfrac{16}{625}\)

h) 5^(x-2)(x+3)=(-17)⁰

i) (x - 2)⁸=(x - 2)⁶

k) (x + 1)⁷=(x + 1)⁵

l) (3x - 1)²ⁿ⁺¹=8²ⁿ⁺¹

Answer 1

a) 27^x : 3^x = 9

(27 : 3)^x = 9

9^x = 9¹

x = 1

b) 25 : 5^x =5

5^x = 25 : 5

5^x = 5¹

x = 1

c) 2 : (x + 2)² = \(\dfrac{1}{18}\)

(x + 2)² = 2 : \(\dfrac{1}{18}\)

(x + 2)² = 36

\(\Rightarrow\left[{}\begin{matrix}x+2=6\\x+2=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=4\\x=-8\end{matrix}\right.\)

d) (5x - 1)² = \(\dfrac{36}{49}\)

(5x - 1)² = \(\left(\dfrac{6}{7}\right)^2\)

Bạn làm tiếp nha, mình có việc bận :v