\(2\frac{x}{7}=\frac{75}{35}\)

\(\frac{2.7+x}{7}=\frac{75}{35}\)

\(\frac{14+x}{7}=\frac{75}{35}\)

\(\frac{5\left(14+x\right)}{35}=\frac{75}{35}\)

=>5 ( 14 + x ) = 75

          14 + x   = 75 : 5

          14 + x   = 15

                  x    = 15 - 14

                  x   = 1

Vậy x =1

a) \(\frac{x+1}{99}+\frac{x+2}{98}=\frac{x+3}{97}+\frac{x+4}{96}\)

\(\Rightarrow\frac{x+1}{99}+1+\frac{x+2}{98}+1=\frac{x+3}{97}+1+\frac{x+4}{96}+1\)

\(\Rightarrow\frac{x+100}{99}+\frac{x+100}{98}-\frac{x+100}{97}-\frac{x+100}{96}=0\)

\(\Rightarrow\left(x+100\right)\left(\frac{1}{99}+\frac{1}{98}-\frac{1}{97}-\frac{1}{96}\right)=0\)

Vì 1/99 + 1/98 - 1/97 - 1/96 khác 0

=> x + 100 = 0 => x = -100

b) \(\frac{x-3}{47}+\frac{x-2}{48}=\frac{x-1}{49}+1\)

\(\Rightarrow\frac{x-3}{47}-1+\frac{x-2}{48}-1=\frac{x-1}{49}+1-2\)

\(\Rightarrow\frac{x-50}{47}+\frac{x-50}{48}-\frac{x-50}{49}=0\)

\(\Rightarrow\left(x-50\right)\left(\frac{1}{47}+\frac{1}{48}-\frac{1}{49}\right)=0\)

Vì 1/47 + 1/48 - 1/49 khác 0

Nên x -50 = 0 => x = 50

\(a,4\frac{3}{x}=\frac{47}{x}\)

\(\frac{4x+3}{x}=\frac{47}{x}\)

\(\Rightarrow4x^2+3x=47x\)

\(4x^2=47x-3x=44x\)

\(4x^2:4x=44x:4x\)

\(x=11\)

\(b,x\frac{x}{15}=\frac{112}{5}\)

\(\frac{15x+x}{15}=\frac{112}{5}\)

\(75x+5x=112.15\)

\(80x=1680\)

\(x=21\)

a,        \(4\frac{3}{x}=\frac{47}{x}\)

   \(\Leftrightarrow\frac{4x+3}{x}=\frac{47}{x}\)

\(\Leftrightarrow4x+3=47\)

                \(4x=47-3\)

                \(4x=44\)

                  \(x=44:4\)

                  \(x=11\)

b,            \(x\frac{x}{15}=\frac{112}{5}\)

\(\Leftrightarrow\frac{15x+x}{15}=\frac{112}{5}\)

        \(\Leftrightarrow\frac{16x}{15}=\frac{336}{15}\)

          \(\Leftrightarrow16x=336\)

                       \(x=336:16\)

                       \(x=21\) 

câu 2

\(...=\sqrt{\left(2-\sqrt{5}\right)^2}-\sqrt{\left(2+\sqrt{5}\right)^2}=\left|2-\sqrt{5}\right|-\left|2+\sqrt{5}\right|=-4\)

câu 1

\(P=\left(\frac{\sqrt{x}}{3+\sqrt{x}}+\frac{x+9}{\left(3-\sqrt{x}\right)\left(3+\sqrt{x}\right)}\right):\left(\frac{3\sqrt{x}+1}{\sqrt{x}\left(\sqrt{x}-3\right)}-\frac{1}{\sqrt{x}}\right)\)

\(=\left(\frac{\sqrt{x}\left(3-\sqrt{x}\right)+x+9}{\left(3+\sqrt{x}\right)\left(3-\sqrt{x}\right)}\right):\left(\frac{3\sqrt{x}+1-\sqrt{x}+3}{\sqrt{x}\left(\sqrt{x}-3\right)}\right)\)

\(=\frac{3\sqrt{x}+9}{\left(3+\sqrt{x}\right)\left(3-\sqrt{x}\right)}:\frac{2\sqrt{x}+4}{\sqrt{x}\left(\sqrt{x}-3\right)}\)

\(=\frac{3}{\left(3-\sqrt{x}\right)}.\frac{\sqrt{x}\left(\sqrt{x}-3\right)}{2\sqrt{x}+4}=\frac{-3\sqrt{x}}{2\sqrt{x}+4}\)

\(P< -1\Leftrightarrow\frac{-3\sqrt{x}}{2\sqrt{x}+4}+1< 0\Leftrightarrow-\sqrt{x}+4< 0\Leftrightarrow\sqrt{x}>4\Leftrightarrow x>16\)

dễ mà bn

a) \(4\frac{3}{x}=\frac{47}{x}\)
=) \(\frac{4x+3}{x}=\frac{47}{x}\)
=) \(4x+3=47\)
=) \(4x=47-3=44\)
=) \(x=44:4=11\)
b) \(x\frac{x}{15}=\frac{112}{5}\)
=) \(\frac{15x+x}{15}=\frac{336}{15}\)
=) \(15x+x=336\)
=) \(16x=336\)
=) \(x=336:16=21\)

Ta có : \(4\frac{3}{x}=\frac{4x+3}{x}=\frac{47}{x}\)

=> 4x +  3 = 47

=> 4x = 44

=> x = 11

mk = 11 bạn ạh

Chúc bạn học giỏi

Giúp mình với các bạn ơi!!!!!!!!!!!!!!!!!!!!!!!!!!!!