=41/10

x - 1/2 = 18/5

x = 18/5 + 1/2

x = 41/10

\(x-\dfrac{1}{2}=\dfrac{3}{5}\times6\)

\(x-\dfrac{1}{2}=\dfrac{18}{5}\)

\(x=\dfrac{18}{5}+\dfrac{1}{2}\)

\(x=\dfrac{41}{10}\)

\(2^x-26=6\\ \Leftrightarrow2^x=32\\ \Leftrightarrow2^x=2^5\\ \Leftrightarrow x=5\)

\(2^x-26=6\)

⇒ \(2^x=6+26=32\)

⇒ \(2^x=32=2^5\)

⇒ \(x=5\)

\(2^x-26=6\)

\(2^x=6+26=32\)

\(2^x=2^5\)

=> x = 5

Vậy x = 5

Thay x=2 và y=-1 vào (d),ta được:

2(m^2-5m+1)+2m-6=-1

=>2m^2-10m+2+2m-6+1=0

=>2m^2-8m-3=0

=>\(m=\dfrac{4\pm\sqrt{22}}{3}\)

\(B=x+y+\dfrac{6}{x}+\dfrac{24}{y}=\left(\dfrac{3x}{2}+\dfrac{6}{x}\right)+\left(\dfrac{3y}{2}+\dfrac{24}{y}\right)-\dfrac{3}{2}\left(x+y\right)\)

\(B\ge2\sqrt{\dfrac{18x}{2x}}+2\sqrt{\dfrac{72y}{2y}}-\dfrac{3}{2}.6=15\)

\(B_{min}=15\) khi \(\left(x;y\right)=\left(2;4\right)\)

Bài 4:

a: =>7/x-5=2

=>x-5=7/2

=>x=17/2

b: =>1-2x=-5

=>2x=6

=>x=3

c: =>2x-3=5 hoặc 2x-3=-5

=>2x=8 hoặc 2x=-2

=>x=-1 hoặc x=4

d: =>2(x+1)^2+17=21

=>2(x+1)^2=4

=>(x+1)^2=2

=>\(x+1=\pm\sqrt{2}\)

=>\(x=\pm\sqrt{2}-1\)

\(\sqrt{x+1}+\sqrt{4x+4}=6\)

\(\Leftrightarrow\sqrt{x+1}+4\sqrt{x+1}=6\)

\(\Leftrightarrow5\sqrt{x+1}=6\)

\(\Leftrightarrow\sqrt{x+1}=\dfrac{6}{5}\)

\(\Leftrightarrow x+1=\left(\dfrac{6}{5}\right)^2\)

\(\Leftrightarrow x+1=\dfrac{36}{25}\)

`<=> x= 11/25`

tất cả số nguyên x >0 là được

Để B>0 thì x+2>0

hay x>-2

a,\(2x-5=3x+15\)

\(3x-2x=-5-15\)

\(x=-20\)

b,\(\frac{2}{x-1}=\frac{6}{x+1}\)

\(2x+2=6x-6\)

\(4x=8\)

\(x=2\)

\(\frac{2x+1}{x-1}=\frac{5.\left(x-1\right)}{x+1}\)

\(\frac{2x+1}{x-1}=\frac{5x-5}{x+1}\)

\(2x^2+3x+1=5x^2-10+5\)

\(3x^2-3x=10-5+1=6\)

\(3x.\left(x-1\right)=6\)

\(x.\left(x-1\right)=3\)

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