Lời giải:

a. $=-(37+63)+[25+(-25)]+(-9)=-100+0+(-9)=-(100+9)=-109$

b. $=[1+(-3)]+[5+(-7)]+....+[21+(-23)]$

$=\underbrace{(-2)+(-2)+....+(-2)}_{6}=(-2).6=-12$

c. $=-(280+20)+[-(79+21)]=-300+(-100)=-(300+100)=-400$

d. $=[-(27+43)]+[-(208+102)]=-70+(-310)=-(70+310)=-380$

e. $=(38+120)-(12+46)=158-58=100$

f. $=9+15+11+24=(9+11)+(15+24)=20+39=59$

=(-48).72+72.(-152)

=72.(-48-152)

=72.(-200)

=-14400

Bài 1

a) \(5\times72\times10\times2=\left(5\times2\times10\right)\times72=100\times72=7200\) 

b) \(40\times125=5\times\left(8\times125\right)=5\times1000=5000\) 

c) \(16\times6\times25=4\times4\times6\times25=\left(4\times6\right)\times\left(4\times25\right)=24\times100=2400\) Bài 2:

a) \(24\times57+43\times24=24\times\left(57+43\right)=24\times100=2400\) 

b) \(12\times19+80\times12+12=12\times\left(19+80+1\right)=12\times100=1200\) 

c) \(\left(36\times15\times169\right)\div\left(5\times18\times13\right)\) 

 \(=\left(18\times2\times3\times5\times13\times13\right)\div\left(5\times18\times13\right)\) 

\(=\left(2\times3\times13\right)\times\left(18\times5\times13\right)\div\left(5\times18\times13\right)\) 

\(=2\times3\times13\)

\(=78\)

d) \(\left(44\times52\times60\right)\div\left(11\times13\times15\right)\) 

\(=\left(4\times11\times4\times13\times4\times15\right)\div\left(11\times13\times15\right)\)

\(=\left(4\times4\times4\right)\times\left(11\times13\times15\right)\div\left(11\times13\times15\right)\)

\(=4\times4\times4\)

\(=64\)

Bài 3:

a) \(x-280\div35=5\times54\) 

                \(x-8=270\) 

                      \(x=270+8\) 

                      \(x=278\) 

b) \(\left(x-280\right)\div35=54\div4\) 

    \(\left(x-280\right)\div35=\dfrac{27}{2}\) 

               \(x-280=\dfrac{27}{2}\times35\) 

                \(x-280=\dfrac{945}{2}\) 

                          \(x=\dfrac{945}{2}+280\) 

                          \(x=\dfrac{1505}{2}\) 

c) \(\left(x-128+20\right)\div192=0\) 

                 \(x-128+20=0\times192\) 

                \(x-128+20=0\) 

                        \(x-128=0-20\) 

                        \(x-128=-20\)

                                  \(x=-20+128\) 

                                 \(x=108\) 

d) \(4\times\left(x+200\right)=460+85\times4\) 

    \(4\times\left(x+200\right)=460+340\) 

    \(4\times\left(x+200\right)=800\) 

             \(x+200=800\div4\) 

             \(x+200=200\) 

                      \(x=200-200\) 

                      \(x=0\) 

Bài 4:

a) \(\dfrac{7}{12}-\dfrac{5}{12}=\dfrac{2}{12}=\dfrac{1}{6}\) 

b) \(\dfrac{8}{11}+\dfrac{19}{11}=\dfrac{27}{11}\) 

c) \(\dfrac{3}{8}+\dfrac{5}{12}=\dfrac{9}{24}+\dfrac{10}{24}=\dfrac{19}{24}\) 

d) \(\dfrac{3}{4}+\dfrac{7}{12}=\dfrac{9}{12}+\dfrac{7}{12}=\dfrac{16}{12}=\dfrac{4}{3}\) 

Bài 5:

a) \(x-\dfrac{6}{7}=\dfrac{5}{2}\) 

           \(x=\dfrac{5}{2}+\dfrac{6}{7}\) 

           \(x=\dfrac{47}{14}\) 

b) \(\dfrac{12}{7}\div x+\dfrac{2}{3}=\dfrac{7}{5}\) 

            \(\dfrac{12}{7}\div x=\dfrac{7}{5}-\dfrac{2}{3}\) 

             \(\dfrac{12}{7}\div x=\dfrac{11}{15}\) 

                       \(x=\dfrac{12}{7}\div\dfrac{11}{15}\) 

                        \(x=\dfrac{180}{77}\)

a) (-4).(-3).(-125). 25.(-8)

= [ -8.( -125)] . (-4.25) . (-3)

=1000. (-100).3

= - 100000 .3

= - 300000

b) 136. (- 47 ) + 36.47

= -136 .47 +36.47

=47.( -136+36)

= 47. ( -100)

= -4700

d)  125.(-24) + 24.125

= 125. ( -24+24)

= 125. 0

=0

a) 125. (- 61 ) . (- 2)³ . ( -1 )²ⁿ

= 125 . (-61) . (-8) . 1

= [ 125 . (-8) ] . [ (-61) . 1 ]

= (-1000) . (-61)

= 61 000

b) 136. ( - 47 ) + 36 .47

= (-136) . 47 + 36 . 47

= 47 . [ (-136) + 36]

= 47 . (-100)

= -4700

c) ( - 48 ). 72 + 36 . ( - 304 )

= (-48) . 2 . 36 + 36 . ( - 304)

= (-96) . 36 + 36. (-304)

= 36 . [ (-96) + (-304) ]

= 36 . (-400)

= -14 400

# HOK TỐT #

a) 125. (- 61 ) . (- 2)³ . ( -1 )²ⁿ ( n thuộc tập N* )

=125 . (-61) . (-8) . 1

=[125.(-8)].(-61)

=-1000.(-61)

=61000

b) 136. ( - 47 ) + 36 .47

=(-136).47+36.47

=47.(-136+36)

=47.(-100)

=-4700

c) ( - 48 ). 72 + 36 . ( - 304 )

=(-48).2.36+36.(-304)

=(-48.2).36+36.(-304)

=-96.36+36.(-304)

=36.[-96+(-304)]

=36.(-400)

=-14400

a) Đặt \(A=125.\left(-61\right).\left(-2\right)^3.\left(-1\right)^{2n}\)

- Ta có: \(A=125.\left(-61\right).\left(-2\right)^3.\left(-1\right)^{2n}\)

      \(\Leftrightarrow A=\left[125.\left(-8\right)\right].\left[\left(-61\right).1\right]\)

      \(\Leftrightarrow A=\left(-1000\right).\left(-61\right)\)

      \(\Leftrightarrow A=61000\)

Vậy \(A=61000\)

b) Đặt \(B=136.\left(-47\right)+36.47\)

- Ta có: \(B=136.\left(-47\right)+36.47\)

      \(\Leftrightarrow B=47.\left[\left(-136\right)+36\right]\)

      \(\Leftrightarrow B=47.\left(-100\right)\)

      \(\Leftrightarrow B=-4700\)

Vậy \(B=-4700\)

c) Đặt \(C=\left(-48\right).72+36.\left(-304\right)\)

- Ta có: \(C=\left(-48\right).72+36.\left(-304\right)\)

      \(\Leftrightarrow C=\left(-48\right).72+72.\left(-152\right)\)

      \(\Leftrightarrow C=72.\left[\left(-48\right)+\left(-152\right)\right]\)

      \(\Leftrightarrow C=72.\left(-200\right)\)

      \(\Leftrightarrow C=-14400\)

Vậy \(C=-14400\)