1.a) 4.(12+88) = 4.100=400

b)7²- 6 .[2.8:8 ]=7²-6.[16:8]=7²-6 .2= 49-12=37  ( tui ko chắc lắm )

2.a) x=26-11=15 

b) (4x-15)³=5³ 

4x-15=5 

4x= 5+15

4x=20

vậy x = 20

Bài 2: 

a: Ta có: x+11=26

nên x=15

b: Ta có: \(\left(4x-15\right)^3=125\)

\(\Leftrightarrow4x-15=5\)

hay x=5

\(\frac{2.6^9.2^5.18^4}{2^2.6^8}=\frac{2.\left(2.3\right)^9.2^5.\left(2.3^2\right)^4}{2^2.\left(2.3\right)^8}=\frac{2.2^9.3^9.2^5.2^4.3^8}{2^2.2^8.3^8}=\frac{2^{19}.3^{17}}{2^{10}.3^8}=2^9.3^9\)

\(=\left(2.3\right)^9=6^9\)

Tính hợp lý

\(\frac{2.6^9.2^5.18^4}{2^2.6^8}=\frac{2^6.2^9.3^9.2^4.3^8}{2^2.2^8.3^8}=\frac{2^{19}.3^{17}}{2^{10}.3^8}=2^9.3^9=6^9\)

học tốt nhé bn

#Tịnh

\(A=\dfrac{5}{4}\cdot\dfrac{18}{5}-\dfrac{5}{4}\cdot\dfrac{7}{5}-\dfrac{5}{4}\cdot\dfrac{1}{5}=\dfrac{5}{4}\cdot\dfrac{10}{5}=\dfrac{10}{4}=\dfrac{5}{2}\)

C =[125.(73-75)]:(-25)2

=125.(-2):(-25).2

=-250:(-50)

=5

E=125.9.(-4).(-8).25.7

=125.(-8).25.(-4).7.9

=-1000.(-100).63

=6300000

C = ( 125 . 73 - 125 . 75 ) : ( -50)

C = 125 .( -2 ) : (-50)

C = -250 : -50

C =  50

G = ( -3 )²+( -5)³: l -5 l

G = 9 + ( -125) : 5

G = 9 + ( -25 )

G= ( -16 )

E = 125 .9.*( -4 ) . ( -8) .25.7

E = 25.5 .( -4 ) .9 .2. ( -4 ) .25 .7

E =( -100 ).10.( -100).63

E = 10000.630

E = 630000

**** mha

`8 2/7-(3 4/9+4 2/7)`

`=8+2/7-(3+4/9+4+2/7)`

`=8+2/7-7-2/7-4/9`

`=1-4/9`

`=5/9`

8 2/7-(3 4/9+4 2/7)

=58/7-31/9-30/7

=(58/7-30/7)-31/9

=4-31/9

=5/9