Question

Tìm x

a) \(2^{3x+2}=4^{x+5}\)

b)\(3^{-1}.3^x+9.3^x=28\)

GIÚP MK NHÉ, MK CẢM ƠN NHIỀU !!!

Answer 1

a) 2^3x+2 = 4^x+5 = (2²)^x+5 = 2^2x+10

=> 3x + 2 = 2x + 10

=> 3x - 2x = 10 - 2

x = 8

b) 3^-1.3^x + 9.3^x = 28

3^x. ( 3^-1 + 9) = 28

3^x. 28/3 = 28

3^x = 3 = 3¹

=> x = 1

Answer 2

     \(2^{3x+2}=4^{x+5}\)

\(\Rightarrow2^{3x+2}=\left(2^2\right)^{x+5}\)

\(\Rightarrow3x+2=2\left(x+5\right)\)

\(\Rightarrow3x+2=2x+10\)

\(\Rightarrow3x-2x=10-2\Rightarrow x=8\)

      \(3^{-1}.3^x+9.3^x=28\)

\(\Rightarrow\frac{1}{3}.3^x+9.3^x=28\)

\(\Rightarrow3^x.\left(9+\frac{1}{3}\right)=28\)

\(\Rightarrow3^x.\frac{28}{3}=28\)

\(\Rightarrow3^x=3\Rightarrow x=1\)

Chúc bạn học tốt.