Question

1.Tìm số hữu tỉ x:

a)\(4^{x+2}.3^x=16.12^5\)\(\)

b)\(\dfrac{3}{2}.4x+\dfrac{5}{3}.4^{x+2}=\dfrac{3}{2}.4^8+\dfrac{5}{3}.4^{10}\)

Answer 1

a) \(4^{x+2}.3^x=16.12^5\)

\(\Leftrightarrow4^{x+2}.3^x=4^2.4^5.3^5\)

\(\Leftrightarrow4^{x-5}.3^{x-5}=1\)

\(\Leftrightarrow12^{x-5}=1\)

\(\Leftrightarrow x-5=0\Leftrightarrow x=5\)

Answer 2

\(a)4^{x+2}.3^x=4^2.\left(4.3\right)^5\)

\(4^{x+2}.3^x=4^7.3^5\)

\(\Rightarrow4^{x+2}=4^7;3^x=3^5\)

\(\Rightarrow x=5\)

Vậy \(x=5\)