Bài làm

a) 3x : 9 = 3⁹¹ 

=> 3x : 3² = 3⁹¹ 

=> 3x        = 3⁹¹ x 3² 

=> 3x        = 3⁹³ 

=>   x        = 3⁹³ : 3

=>   x        = 3⁹² 

Vậy x = 3⁹² 

b) 81 : 3x + 1 = 9

    81 : 3x       = 9 - 1

    81 : 3x       = 8

           3x       = 81 : 8

           3x       = 10,125

             x       = 10,125 : 3

             x       = 3,375

Vậy x = 3,375

# Học tốt #

a ) \(3x:9=3^{91}\)

\(\Rightarrow3x:3^2=3^{91}\)

\(3x=3^{91}.3^2\)

\(3x=3^{93}\)

\(x=3^{93}:3\)

\(x=3^{92}\)

Vậy \(x=3^{92}\)

b ) \(81:3x+1=9\)

        \(27x+1=9\)

         \(27.x=9-1\)

          \(27.x=8\)

              \(x=8:27\)

                  \(x=\frac{8}{27}\)

    Vậy \(x=\frac{8}{27}\)

        Chúc bạn học tốt !!!

Vì \(\left|\frac{1}{3}-x\right|\ge0\)

\(\Rightarrow5+\left|\frac{1}{3}+x\right|\ge5\)

Dấu " = " xảy ra khi :

\(\left|\frac{1}{3}+x\right|=0\)

\(\Rightarrow x=-\frac{1}{3}\)

Vậy \(Min_A=5\Leftrightarrow x=-\frac{1}{3}\)

Study well 

\(52^{35}=52^{32}.52^3=52^{4n}.\left(.....8\right)=\left(.....6\right).\left(.....8\right)=\left(.....8\right)\)

\(2007^{2007}=2007^{2004}.2007^3=2007^{4n}.\left(.....3\right)=\left(.....1\right).\left(.....3\right)=\left(.....3\right)\)

Xét \(\Delta ABC\)có

   \(\widehat{A}+\widehat{B}+\widehat{C}=180^o\)

Hay \(\widehat{B}+\widehat{C}=180^o-50^o\)

\(\widehat{B}+\widehat{C}=130^o\)

Suy ra :

    \(\widehat{B}=\frac{130^o+20^o}{2}=75^o\)

\(\widehat{C}=75^o-20^o=55^o\)

     Vậy \(\widehat{B}=75^o;\widehat{C}=55^o\)

mk mới lp 6

\(\left|a\right|=1,5\Rightarrow\orbr{\begin{cases}a=1,5\\a=-1,5\end{cases}}\)

\(Th1:a=1,5;b=-0,75\)hay \(a=\frac{3}{2};b=\frac{-3}{4}\)

\(\Rightarrow M=\frac{3}{2}+2.\frac{3}{2}.\frac{-3}{4}-\frac{-3}{4}\)

\(=\frac{6}{4}+\frac{-9}{4}+\frac{3}{4}=0\)

\(Th2:a=-1,5;b=0,75\)hay \(a=\frac{-3}{2};b=\frac{-3}{4}\)

​\(\Rightarrow M=\frac{-3}{2}+2.\frac{-3}{2}.\frac{-3}{4}-\frac{-3}{4}\)​

\(=\frac{-6}{4}+\frac{9}{4}+\frac{3}{4}=\frac{3}{2}\)

4.3 - ( - 1.2) 

= 4.3 + 1.2

= 5.5

Học tốt :) 

4,3-(-1,2)

= 4,3+1,2

=5,5