Question

Tìm x , y:

a , \(\dfrac{2}{3}.3^{x+1}-7.3^x=405\)

b , \(\left(0,4x-1,3\right)^2=5,29\)

c , \(5.2^{x+1}.2^{-2}-2^x=384\)

d , \(4^x+4^{x+3}=4160\)

e , \(2^{x-1}+5.2^{x-2}=\dfrac{7}{32}\)

Answer 1

a: \(\Leftrightarrow3^x\cdot\left(\dfrac{2}{3}\cdot3-7\right)=405\)

\(\Leftrightarrow3^x=-81\)(vô lý)

b: \(\left(0,4x-1,3\right)^2=5,29\)

=>0,4x-1,3=2,3 hoặc 0,4x-1,3=-2,3

=>0,4x=3,6 hoặc 0,4x=-1

=>x=9 hoặc x=-2,5

c: \(5\cdot2^{x+1}\cdot2^{-2}-2^x=284\)

\(\Leftrightarrow2^x\cdot5\cdot2\cdot2^{-2}-2^x=284\)

\(\Leftrightarrow2^x\cdot\left(\dfrac{5}{2}-1\right)=284\)

\(\Leftrightarrow2^x=\dfrac{568}{3}\)(vô lý)

d: \(\Leftrightarrow4^x\left(1+4^3\right)=4160\)

\(\Leftrightarrow4^x=64\)

hay x=3