Question

Tìm x biết :

a) 81 * 3^ x+1= 3^20

Dấu * là nhân nha nhanh tớ tick

Answer 1

\(3^4.3^{x+1}=3^{20}\)

\(3^{x+5}=3^{15+5}\)

\(=>x=15\)

Vậy x=15

Answer 2

\(81\cdot3^{x+1}=3^{20}\)

\(3^4\cdot3^x\cdot3=3^{20}\)

\(3^5\cdot3^x=3^{20}\)

\(3^x=3^{20}:3^5=3^{15}\)

\(\Rightarrow x=15\)

Answer 3

a) 81 . 3^x+1 = 3²⁰

=> 3⁴ . 3^x+1 = 3²⁰

=> 3⁴ . 3^x . 3= 3²⁰

=> 3⁴ . 3 . 3^x = 3²⁰

=> 3⁵ . 3^x = 3²⁰

=> 3^x = 3²⁰ : 3⁵

=> 3^x = 3¹⁵

=> x = 15