\(\frac{2}{5}\times\frac{3}{4}\times\frac{6}{15}:\frac{4}{9}\times5=\frac{2\times3\times6\times9\times5}{5\times4\times15\times4}=\frac{27}{20}\)

2/5 x 3/4 x 6/15 : 4/9 x 5 = 6/20 x 6/15 : 4/9 x 5 = 36/300 : 4/9 x 5 = 324/1200 x 5 = 1620/1200

4 + 4 x 2 + 4 x 3 + 4 x 4 = ( 4 x 2 + 4 x 3 ) + (4 x 4 + 4) 

                                      =   20 + 20 

                                        = 40 

5 + 5 x 2 + 5 x 3 + 5 x 4 = (5 x 4 + 5 x 2 ) + ( 5 x 3 + 5 )

                                      = 30 + 20 

                                     = 50

730971

809703

a) Thu gọn và sắp xếp:

\(P\left(x\right)=x^2+5x^4-3x^3+x^2+4x^4+3x^3-x+5\)

\(P\left(x\right)=\left(5x^4+4x^4\right)-\left(3x^3-3x^3\right)+\left(x^2+x^2\right)-x+5\)

\(P\left(x\right)=9x^4+2x^2-x+5\)

\(Q\left(x\right)=x-5x^3-x^2-x^4+4x^3-x^2+3x-1\)

\(Q\left(x\right)=x^4-\left(5x^3-4x^3\right)-\left(x^2+x^2\right)+\left(x+3x\right)-1\)

\(Q=x^4-x^3-2x^2+4x-1\)

b) \(P\left(x\right)+Q\left(x\right)\)

\(=\left(9x^4+2x^2-x+5\right)+\left(x^4-x^3-2x^2+4x-1\right)\)

\(=9x^4+2x^2-x+5+x^4-x^3-2x^2+4x-1\)

\(=\left(9x^4+x^4\right)-x^3+\left(2x^2-2x^2\right)-\left(x-4x\right)+\left(5-1\right)\)

\(=10x^4-x^3+3x+4\)

\(P\left(x\right)-Q\left(x\right)\)

\(=\left(9x^4+2x^2-x+5\right)-\left(x^4-x^3-2x^2+4x-1\right)\)

\(=9x^4+2x^2-x+5-x^4+x^3+2x^2-4x+1\)

\(=\left(9x^4-x^4\right)+x^3+\left(2x^2+2x^2\right)-\left(x+4x\right)+\left(5-1\right)\)

\(=8x^4+x^3+4x^2-5x+4\)

4 x 1 = 4                                                4 x 6 = 24

4 x 2 = 8                                                4 x 7 = 28

4 x 3 = 12                                              4 x 8 = 32

4 x 4 = 16                                              4 x 9 = 36

4 x 5 = 20                                              4 x 10 = 40

4 x 1 = 4

4 x 2 = 8

4 x 3 = 12

4 x 4 = 16

4 x 5 = 20

4 x 6 = 24

4 x 7 = 28

4 x 8 = 32

4 x 9 = 36

4 x 10 = 40

4 x 1 = 4

4 x 2 = 8

4 x 3 =12

4 x 4 = 16

4 x 5 = 20

4 x 6 = 24 

4 x 7 = 28 

4 x 8 = 32

4 x 9 = 36

4 x 10 = 40

1,

a, \(x\)x 124= 4829-365

 \(x\)x 124 = 4464

\(x\)= 4464 :124

\(x\)= 36.

b,\(x\)x 137 = 25 x 3 

   \(x\)x 137 = 75

\(x\)= \(\frac{75}{137}\)

2,

\(\frac{4}{5}\)x\(\frac{3}{7}+\frac{4}{5}\)x\(\frac{6}{7}-\frac{4}{5}\)x\(\frac{4}{10}\)

=\(\frac{4}{5}\)x\(\left(\frac{3}{7}+\frac{6}{7}-\frac{4}{10}\right)\)=\(\frac{4}{5}\)x\(\frac{31}{35}\)\(\frac{124}{175}\)

\(\text{Bài }1\text{ : Tìm }x\text{ : }\)

\(a,\text{ }x\text{ x }124=4829-365\)

     \(x\text{ x }124=4464\)

     \(x=4464\text{ : }124\)

     \(x=36\)

\(b,\text{ }x\text{ x }137=25\text{ x }3\)

     \(x\text{ x }137=75\)

     \(x=75\text{ : }137\)

     \(x=\frac{75}{137}\)

\(\text{Bài }2\text{ : Tính bằng cách thuận tiện nhất : }\)

      \(\frac{4}{5}\text{ x }\frac{3}{7}+\frac{4}{5}\text{ x }\frac{6}{7}-\frac{4}{5}\text{ x }\frac{4}{10}\)

\(=\frac{4}{5}\text{ x }\left(\frac{3}{7}+\frac{6}{7}-\frac{4}{10}\right)\)

\(=\frac{4}{5}\text{ x }\left(\frac{9}{7}-\frac{4}{10}\right)\)

\(=\frac{4}{5}\text{ x }\frac{31}{35}\)

\(=\frac{124}{175}\)

mẹ ơi dễ thế để con giải cho:

Bài 1:

a. X x 124=4829-365

    X x 124         =4464

    X                  = 4464:124

    X                 =36

b tương tự như câu a

Bài 2:

\(\frac{4}{5}\)x \(\frac{3}{7}\)+\(\frac{4}{5}\)x \(\frac{6}{7}\)-\(\frac{4}{5}\)x \(\frac{4}{10}\)

=\(\frac{4}{5}\)x(\(\frac{6}{7}\)+ \(\frac{3}{7}\)-\(\frac{4}{10}\))

= \(\frac{4}{5}\)x \(\frac{31}{35}\)

\(\frac{124}{175}\)