a) ĐKXĐ: x≠ \(\dfrac{1}{2}\); x≠ \(\dfrac{-1}{2}\); x≠0

    A= \(\left(\dfrac{1}{2x-1}+\dfrac{3}{1-4x^2}-\dfrac{2}{2x+1}\right):\dfrac{x^2}{2x^2+x}\)

       = \(\left(\dfrac{2x+1-3-2\left(2x-1\right)}{4x^2-1}\right):\dfrac{x^2}{2x^2+x}\)

       =  \(\left(\dfrac{2x+1-3-4x+2}{4x^2-1}\right):\dfrac{x^2}{2x^2+x}\)

       = \(\dfrac{-4x}{\left(2x+1\right)\left(2x-1\right)}.\dfrac{x\left(2x+1\right)}{x^2}\)

       =  \(\dfrac{-4x^2}{x^2\left(2x-1\right)}\)

       = \(\dfrac{-4}{2x-1}\)

b) Tại x= -2 ta có A= \(\dfrac{-4}{2.\left(-2\right)-1}\)= \(\dfrac{4}{5}\)

c)  A= 4 ta có \(\dfrac{-4}{2x-1}\)=4

                  ⇔ -4 = 4(2x-1)

                  ⇔ -4 = 8x-4 

                   ⇔ x = 0

d)  A=1 ta có \(\dfrac{-4}{2x-1}\)=1

                   ⇔  -4 = 2x-1

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

10.213

11. 2 giờ 55 phút

12. 4 ngày 21 giờ

13.

a: 6,008

b: 4500

c: 5,628

d: 4,009

14.

a,8579 cm2

b,32,04 m2

c,187200m2

d,5,017 tấn

14:

a: \(85.79km^2=857900000000cm^2\)

b: \(32m^24dm^2=32.04m^2\)

c: \(1872dm^2=18.72m^2\)

d: 5 tấn 17kg=5,017 tấn

13:

a: \(6dm^38cm^3=6.008dm^3\)

b: \(4.5m^3=4500dm^3\)

c: \(5628dm^3=5.628m^3\)

d: \(4m^39dm^3=4.009m^3\)

12: =108h:3+80h

=36h+80h=116h

10:

3h18p+7h21p:3

=198p:441p:3

=198p+147p=345p

a) Tính giá trị của A. Khi x=\(\frac{1}{4}\)là : 

\(\frac{\sqrt{\frac{1}{4}}-5}{\sqrt{\frac{1}{4}}+3}=-2,634825932\)

a)-9/7

A đâu em?

\(A=\dfrac{x}{\sqrt{x}+1}+\dfrac{\sqrt{x}+2x}{x+\sqrt{x}}\)

a: \(A=\sqrt{x}+\dfrac{\sqrt{x}\left(1+2\sqrt{x}\right)}{\sqrt{x}\left(\sqrt{x}+1\right)}=\sqrt{x}+\dfrac{2\sqrt{x}+1}{\sqrt{x}+1}\)

Khi x=4 thì \(A=2+\dfrac{2\cdot2+1}{2+1}=2+\dfrac{5}{3}=\dfrac{11}{3}\)

b: Khi x=(2-căn 3)^2 thì \(A=2-\sqrt{3}+\dfrac{2\left(2-\sqrt{3}\right)+1}{2-\sqrt{3}+1}\)

\(=2-\sqrt{3}+\dfrac{4-2\sqrt{3}+1}{3-\sqrt{3}}\)

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

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

\(=\dfrac{6-2\sqrt{3}-3\sqrt{3}+3+5-2\sqrt{3}}{3-\sqrt{3}}\)

\(=\dfrac{14-7\sqrt{3}}{3-\sqrt{3}}\)

d: A=2

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

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

=>\(x+\sqrt{x}-1=0\)

=>\(\left[{}\begin{matrix}\sqrt{x}=\dfrac{-1+\sqrt{5}}{2}\left(nhận\right)\\\sqrt{x}=\dfrac{-1-\sqrt{5}}{2}\left(loại\right)\end{matrix}\right.\Leftrightarrow x=\dfrac{6-2\sqrt{5}}{4}=\dfrac{3-\sqrt{5}}{2}\)

a: Khi x=2 và y=-3 thì \(x^2+2y=2^2+2\cdot\left(-3\right)=4-6=-2\)

b: \(A=x^2+2xy+y^2=\left(x+y\right)^2\)

Khi x=4 và y=6 thì \(A=\left(4+6\right)^2=10^2=100\)

c: \(P=x^2-4xy+4y^2=\left(x-2y\right)^2\)

Khi x=1 và y=1/2 thì \(P=\left(1-2\cdot\dfrac{1}{2}\right)^2=\left(1-1\right)^2=0\)