\(\left[\frac{4}{7}-\frac{1}{2}.x\right]^3=2^3\)

\(\Rightarrow\frac{4}{7}-\frac{1}{2}.x=2\)

\(\frac{1}{2}.x=-\frac{10}{7}\)

\(x=-\frac{20}{7}\)

tks bạn nhiều

làm phiền cho mk hỏi câu này với nếu ko biết thì thôi:so sánh:\(\frac{2^{23}+1}{2^{25}+1}va\frac{2^{25}+1}{2^{27}+1}\)

`-2/5 : x=1/2`

`=> x= -2/5 : 1/2`

`=> x= -2/5 xx 2`

`=>x= -4/5`

__

`7/6 : x = 7/4`

`=>x= 7/6 : 7/4`

`=>x=7/6 xx 4/7`

`=>x= 28/42`

`=>x=2/3`

tìm x hả

\(x=\dfrac{-2}{5}:\dfrac{1}{2}\)

\(x=\dfrac{-4}{5}\)

b. \(x=\dfrac{7}{6}:\dfrac{7}{4}\)

\(x=\dfrac{2}{3}\)

\(\sqrt{13+\sqrt{48}}=\sqrt{13+\sqrt{4.12}}=\sqrt{13+2\sqrt{12}}=\sqrt{\left(\sqrt{12}+1\right)^2}\)

\(=\sqrt{12}+1=2\sqrt{3}+1\)

\(\Rightarrow\sqrt{5-\sqrt{13+\sqrt{48}}}=\sqrt{5-2\sqrt{3}-1}=\sqrt{4-2\sqrt{3}}=\sqrt{\left(\sqrt{3}-1\right)^2}\)

\(=\sqrt{3}-1\)

\(\Rightarrow\sqrt{3+\sqrt{5-\sqrt{13+\sqrt{48}}}}=\sqrt{3+\sqrt{3}-1}=\sqrt{2+\sqrt{3}}\)

\(\Rightarrow\sqrt{\dfrac{4+2\sqrt{3}}{2}}=\sqrt{\dfrac{\left(\sqrt{3}+1\right)^2}{2}}=\dfrac{\sqrt{3}+1}{\sqrt{2}}\)

\(\Rightarrow2\sqrt{3+\sqrt{5-\sqrt{13+\sqrt{48}}}}==2.\dfrac{\sqrt{3}+1}{\sqrt{2}}=\sqrt{6}+\sqrt{2}\)

2) biến đổi khúc sau như câu 1:

\(\Rightarrow\sqrt{6+2\sqrt{5-\sqrt{13+\sqrt{48}}}}=\sqrt{6+2\left(\sqrt{3}-1\right)}=\sqrt{4+2\sqrt{3}}\)

\(=\sqrt{\left(\sqrt{3}+1\right)^2}=\sqrt{3}+1\)

4) Ta có: \(\sqrt{30-2\sqrt{16+6\sqrt{11+4\sqrt{4-2\sqrt{3}}}}}\)

\(=\sqrt{30-2\sqrt{16+6\sqrt{11+4\left(\sqrt{3}-1\right)}}}\)

\(=\sqrt{30-2\sqrt{16+6\sqrt{7+4\sqrt{3}}}}\)

\(=\sqrt{30-2\sqrt{16+6\left(2+\sqrt{3}\right)}}\)

\(=\sqrt{30-2\sqrt{28+6\sqrt{3}}}\)

\(=\sqrt{30-2\left(3\sqrt{3}+1\right)}\)

\(=\sqrt{28-6\sqrt{3}}=3\sqrt{3}-1\)

5) Ta có: \(\dfrac{\left(5\sqrt{3}+\sqrt{50}\right)\left(5-\sqrt{24}\right)}{\sqrt{75}-5\sqrt{2}}\)

\(=\dfrac{5\left(\sqrt{3}+\sqrt{2}\right)\left(\sqrt{3}-\sqrt{2}\right)^2}{\sqrt{75}-5\sqrt{2}}\)

\(=\dfrac{5\left(\sqrt{3}-\sqrt{2}\right)}{5\left(\sqrt{3}-\sqrt{2}\right)}=1\)

2/3.x + 1/4 = 7/12

2/3.x           = 7/12 - 1/4

2/3.x           = 1/3

x                 = 1/3 : 2/3

x                 = 1/2

Bài làm

\(\frac{2}{3}x+\frac{1}{4}=\frac{7}{12}\)

\(\frac{2}{3}x=\frac{7}{12}-\frac{1}{4}\)

\(\frac{2}{3}x=\frac{7}{12}-\frac{3}{12}\)

\(\frac{2}{3}x=\frac{4}{12}\)

\(\frac{2}{3}x=\frac{1}{3}\)

\(x=\frac{1}{3}:\frac{2}{3}\)

\(x=\frac{1}{3}.\frac{3}{2}\)

\(x=\frac{1}{2}\)

Vậy \(x=\frac{1}{2}\)

2/3 .x + 1/4 = 7/12

2/3 .x         = 7/12 - 1/4

2/3.x          = 1/3

x                = 1/3 : 2/3

x                = 1/2

\(\frac{1}{2}\left(\frac{4}{9}-x\right)-\frac{3}{2}\left(16-x\right)+\frac{1}{2}\left(5x+10\right)=0\)

\(\Leftrightarrow\frac{2}{9}-\frac{1}{2}x-24+\frac{3}{2}x+\frac{5}{2}x+5=0\)

\(\Leftrightarrow-\frac{169}{9}=\frac{7}{2}x\Leftrightarrow x=-\frac{338}{63}\)

Sai thì thông cảm cho mk nha

câu a+b dùng quy tắc chuyển vế

c, 3.(1/2-x)-5.(x-1/10)=-7/4

=>(3.1/2-3x)-(5x-5.1/10)=-7/4

=>3/2-3x-5x+1/2=-7/4

=>(3/2+1/2)-(3x+5x)=-7/4

=> 2-8x=-7/4

=>8x=15/4

=>x=15/4:8

=>x=15/32

a) 2.(1/4 - 3x) = 1/5 - 4x
=> 1/2 - 6x = 1/5 -4x
=> -6x + 4x = 1/5 - 1/2
=> -2x         = -3/10 = 3/20
b) 4.(1/3 - x) + 1/2 = 5/6 +x 
=> 4/3 - 4x + 1/2 = 5/6 +x
=> -4x - x = 5/6 - 4/3 - 1/2
=> -5x = -1
=> x= 1/5
c) 3. (1/2 - x) -5. ( x - 1/10) = -7/4
=> 3/2 - 3x - 5x + 1/2 = -7/4
=> -3x - 5x = -7/4 - 3/2 - 1/2 
=> -8x = -15/4
=> x = 15/32

mình chịu

5) Ta có: \(\dfrac{\left(5\sqrt{3}+\sqrt{50}\right)\left(5-\sqrt{24}\right)}{\sqrt{75}-5\sqrt{2}}\)

\(=\dfrac{5\left(\sqrt{3}+\sqrt{2}\right)\left(\sqrt{3}-\sqrt{2}\right)^2}{5\left(\sqrt{3}-\sqrt{2}\right)}\)

=1

tham khảo:

99/100