Question

Tìm x biết :

a) \(\frac{1}{4}\) - \(\frac{1}{3}\)x = \(\frac{2}{5}\) - \(\frac{3}{2}\)x

b) 5 . \(2^{x-2}\) + 3 . \(2^x\) =  \(2^{2016}\) . 17

c) ( \(\frac{1}{2}\) - \(\frac{1}{6}\) ) . \(3^{x+4}\) - 4 . \(3^x\) = \(3^{16}\) - 4 . \(3^{13}\)

Các bn ơi giúp mình với mình cảm trước nha

Answer 1

a)\(\frac{1}{4}-\frac{1}{3}x=\frac{2}{5}-\frac{3}{2}x\)

\(\Leftrightarrow\)\(\frac{15-20x}{60}=\frac{24-90x}{60}\)

\(\Leftrightarrow15-20x=24-90x\)

\(\Leftrightarrow-20x+90x=24-15\)

\(\Leftrightarrow70x=9\)

\(\Leftrightarrow x=\frac{9}{70}\)

 

Answer 2

c) (1/2-1/6)*3^x+4-4*3^x=3^16-4*3^13

=1/3*3^x*3^4-4*3^x=3^13*3^3-4*3^13

=27*3^x-4*3^x=3^13*(27-4)

=3^x*(27-4)=3^13*(27-4)

=>x=13

Answer 3

c,                        \(\frac{1}{3}\)x\(3^x\)x\(3^4\)-4x\(3^x\)=\(3^{16}\)-4x\(3^{13}\)

                    \(\Leftrightarrow\)    \(3^3\)x\(3^x\)-4x\(3^x\)=\(3^3\)x\(3^{13}\)-4x\(3^{13}\)

                   \(\Leftrightarrow\)      \(3^x\)x(\(3^3\)-4)=\(3^{13}\)x(\(3^3\)-4)

                    \(\Leftrightarrow\)         \(3^x\)=\(3^{13}\)

                    \(\Leftrightarrow\)        \(\chi\)=13