A. 2/3 + 3/5 = 19/15

B. 4 và 1/4 - 0,25 = 4 

C. 12 . 2 và 1/3 = 28

D. 8 và 2/7 + 4 và 3/5 + 1 và 5/7 + 5 và 2/5

=   58/7 + 23/5 + 12/7 + 27/5

=   ( 27/5 + 12/5 ) + ( 58/7 + 12/7 )

=   39/5 + 10

=   89/5

=  39/5 + 70/7

Trước hết ta có \(\left(\dfrac{x}{y}\right)^{-z}=\dfrac{1}{\left(\dfrac{x}{y}\right)^z}=\dfrac{1}{\dfrac{x^z}{y^z}}=\dfrac{y^z}{x^z}\)

Suy ra:

\(A=\left(0,25\right)^{-1}\cdot\left(\dfrac{1}{4}\right)^{-2}\cdot\left(\dfrac{4}{3}\right)^{-2}\cdot\left(\dfrac{5}{4}\right)^{-1}\cdot\left(\dfrac{2}{3}\right)^{-3}\)

\(A=\left(\dfrac{1}{4}\right)^{-1}\cdot\left(\dfrac{1}{4}\right)^{-2}\cdot\left(\dfrac{4}{3}\right)^{-2}\cdot\left(\dfrac{5}{4}\right)^{-1}\cdot\left(\dfrac{2}{3}\right)^{-3}\)

\(A=4\cdot4^2\cdot\dfrac{3^2}{4^2}\cdot\dfrac{4}{5}\cdot\dfrac{3^3}{2^3}=4^2\cdot3^5\text{​​}\div5\div2^3\)

\(A=2^4\div2^3\cdot3^5\div5=2\cdot3^5\div5=2\cdot243\div5=\dfrac{486}{5}\)

X×0,75+X×0,25=5

2Xx(0,75+0,25)=5

               2Xx1=5

                  2X=5:1

                  2X=5

                    X=5:2

                    X=5/2

Vậy x=5/2

Bài làm

      \(4x5x0,25x\frac{1}{5}x\frac{1}{2}x2\)

\(=4x5x0,25x0,2x0,5x2\)

\(=\left(4x0,25\right)x\left(5x0,2\right)x\left(0,5x2\right)\)

\(=1x1x1\)

\(=1\)

# Chúc bạn học tốt #

`4 xx 0,25 xx 5 xx 1/5 xx 2 xx 1/2`

`=(4xx0,25) xx(5xx1/5) xx (2xx1/2)`

`= 1 xx 5/5 xx 2/2`

`= 1 xx 1 xx 1`

`=1`

`@ M``i``n`

=1*1*1=1

\(1,\left[\left(-\dfrac{2}{5}\right)+\dfrac{1}{3}\right]-\left(\dfrac{3}{5}-\dfrac{1}{3}\right)=-\dfrac{2}{5}+\dfrac{1}{3}-\dfrac{3}{5}+\dfrac{1}{3}\\ =\left(-\dfrac{2}{5}-\dfrac{3}{5}\right)+\left(\dfrac{1}{3}+\dfrac{1}{3}\right)\\ =\dfrac{-2-3}{5}+\dfrac{1+1}{3}\\ =-\dfrac{5}{5}+\dfrac{2}{3}\\ =-1+\dfrac{2}{3}\\ =\dfrac{-3+2}{3}=-\dfrac{1}{3}\\ b,\left(\dfrac{3}{2}-\dfrac{3}{4}\right)-\left(0,25+\dfrac{1}{2}\right)\\ =\left(\dfrac{3}{2}-\dfrac{3}{4}\right)-\left(\dfrac{1}{4}+\dfrac{1}{2}\right)\\ =\dfrac{3}{2}-\dfrac{3}{4}-\dfrac{1}{4}-\dfrac{1}{2}\\ =\left(\dfrac{3}{2}-\dfrac{1}{2}\right)+\left(-\dfrac{3}{4}-\dfrac{1}{4}\right)\\ =\dfrac{3-1}{2}+\dfrac{-3-1}{4}\\ =\dfrac{2}{2}-\dfrac{4}{4}=1-1=0\)

1: =-2/5+1/3-3/5+1/3

=-1+2/3=-1/3

2: =3/2-3/4-1/4-1/2

=1-1=0

`4xx5xx0,25xx1/5xx1/2xx2`

`=4xx5xx1/4xx1/5xx1/2xx2`

`=[4xx5xx2]/[4xx5xx2]=1`