Mọi người ơi, giúp em với ạ

a) \(\left(9^4.8+9^4.5\right):\left(9^2.\left(10-1\right)\right)\)

=\(9^4.13:9^3=13.9=117\)

b) 100-(75-25)=100-50=50

\(a,\left(2^3\cdot9^4+9^3\cdot45\right):\left(9^2\cdot10-9^2\right)\)

\(< =>\left(8\cdot6561+729\cdot45\right):\left(81\cdot10-81\right)\)

\(< =>\left(52488+32805\right):\left(810-81\right)\)

\(< =>85293:729\)

\(< =>117\)

\(b,100-\left[75-\left(7-2\right)^2\right]\)

\(< =>100-\left[75-\left(5\right)^2\right]\)

\(< =>100-\left[75-25\right]\)

\(< =>100-50\)

\(< =>50\)

\(c,\left(20\cdot2^4+12\cdot2^4\right)-\left(48\cdot2^2\right):8^2\)

\(< =>\left[2^4\cdot\left(20+12\right)\right]-\cdot\left(48\cdot4\right):8^2\)

\(< =>\left[2^4\cdot32\right]-192:8^2\)

\(< =>\left[16\cdot32\right]-192:64\)

\(< =>512-3\)

\(< =>509\)

a)500-{5.[409-(21-2\(^3\).3)\(^2\)+10\(^3\)}:15

=500-{5.[409-(21-24)\(^2\)]+10\(^3\)}:15

=500-{5.[409-(-3)\(^2\)]+10\(^3\)}:15

=500-{5.400+10\(^3\)}:15

=500-{2000+1000}:15

=500-3000:15

=500-200

=300

b)-7129+1478+7129-1479

=[(-7129)+7129]+(1478-1479)

=0+-1

=-1

c)19-42.(-19)+19.(-3)

=19-(-798)+(-57)

=817+(-57)

=760

hok tốt

Đề bài mình viết thiếu là CM biểu thức sau không phụ thuộc vào x ( nghĩa là kết quả phải ra số tự nhiên không có x ) 

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

\(=2x^2-2x+x-1-2x^2-4x+5x-15+4\)

\(=-12\left(đpcm\right)\)

\(B=\left(4x+3\right)\left(2x-5\right)-\left(8x+1\right)\left(x+3\right)+13\left(3x+1\right)+2\)

\(=8x^2-20x+6x-15-\left(8x^2+24x+x+3\right)+39x+13+2\)

\(=-3\left(đpcm\right)\)

a ) Ta có : - 12 . ( x - 5 ) + 7( 3 - x ) = 5

Suy ra - 12x - ( - 12 ) . 5 + 7 . 3 - 7x = 5

Suy ra - 12x + 60 + 21 - 7x = 5

Suy ra - 12x - 7x = 5 - 60 - 21

Suy ra - 19x = - 76

Suy ra x = -76 : ( - 19 )

Vậy x = 4

b ) Ta có : 30 . ( x + 2 ) - 6  . ( x - 5 ) - 24x = 100

Suy ra 30x + 30 . 2 - 6x - ( - 6 ) . 5 - 24x = 100

Suy ra 30x + 60 - 6x + 30 - 24x = 100

Suy ra 30x - 6x - 24x = 100 - 60 - 30

Suy ra 0x = 10

Vậy x = 0

câu a+b dùng quy tắc chuyển vế

c, 3.(1/2-x)-5.(x-1/10)=-7/4

=>(3.1/2-3x)-(5x-5.1/10)=-7/4

=>3/2-3x-5x+1/2=-7/4

=>(3/2+1/2)-(3x+5x)=-7/4

=> 2-8x=-7/4

=>8x=15/4

=>x=15/4:8

=>x=15/32

a) 2.(1/4 - 3x) = 1/5 - 4x
=> 1/2 - 6x = 1/5 -4x
=> -6x + 4x = 1/5 - 1/2
=> -2x         = -3/10 = 3/20
b) 4.(1/3 - x) + 1/2 = 5/6 +x 
=> 4/3 - 4x + 1/2 = 5/6 +x
=> -4x - x = 5/6 - 4/3 - 1/2
=> -5x = -1
=> x= 1/5
c) 3. (1/2 - x) -5. ( x - 1/10) = -7/4
=> 3/2 - 3x - 5x + 1/2 = -7/4
=> -3x - 5x = -7/4 - 3/2 - 1/2 
=> -8x = -15/4
=> x = 15/32

mình chịu

\(a)-129+\left[4^2\cdot5-(-7)\right]:3\)

\(=-129+\left[16\cdot5-(-7)\right]:3\)

\(=-129+\left[16\cdot5+7\right]:3\)

\(=-129+\left[80+7\right]:3\)

\(=-129+\frac{87}{3}\)

\(=-129+29=-100\)

\(b)-(-2014-879)+\left[1136+(-2014)\right]\)

\(=(2014+879)+\left[1136-2014\right]\)

\(=2893+(-878)\)

\(=2893-878=2015\)

\(\text{Câu 2 : Tìm số nguyên x biết :}\)

\(a)(\left|x\right|+3):5-3=12\)

\(\Rightarrow(\left|x\right|+3):5=12+3\)

\(\Rightarrow(\left|x\right|+3):5=15\)

\(\Rightarrow(\left|x\right|+3)=15\cdot5\)

\(\Rightarrow(\left|x\right|+3)=75\)

\(\Rightarrow\left|x\right|=75-3\)

\(\Rightarrow\left|x\right|=72\)

\(\Rightarrow x\in\left\{72;-72\right\}\)

\(b)\frac{86}{2(2x-1)^2-7}+4^2=2\cdot3^2\)

\(\Rightarrow\frac{86}{2(2x-1)^2-7}+16=2\cdot9\)

\(\Rightarrow\frac{86}{2(2x-1)^2-7}+16=18\)

\(\Rightarrow\frac{86}{8x^2-8x-5}=18-16\)

\(\Rightarrow\frac{86}{8x^2-8x-5}=2\)

....

\(\text{Còn nốt bạn tự làm nhé :3}\)

\(-129+\left[4^2\cdot5-\left(-7\right)\right]:3\)

\(=-129+\left[80+7\right]:3\)

\(=-129+29\)

\(=-100\)

\(-\left(-214-879\right)+\left[1136+\left(-2014\right)\right]\)

\(2893+\left(-878\right)\)

\(2015\)

bn lớp mấy vậy