(1-2+3-4+5-6+7-8+...+101-102+103) * x-120=2012

[ -1 + ( -1 ) ... ( -1 ) + 103] * x -120 = 2012

( -1 x 51 + 103 ) * x - 120 = 2012

( -51 +103) * x = 2012 + 120

52 * x =2132

x= 2132 : 52

x= 41

a, 60

b, 15

c, 11

d, 11

e, 110

g, 5

làm hẳn ra nha bn 

\(a,120-\left(x-135\right)=300\)

\(x-135=120-300\)

\(x-135=-180\)

\(x=-180+135\)

\(x=-45\)

\(b,\left(102-3x\right):3=-19\)

\(102-3x=\left(-19\right)\times3\)

\(102-3x=57\)

\(3x=102-57\)

\(3x=45\)

\(x=15\)

a) 120 - ( x - 135 ) = 300

=> x - 135 = 120 - 300

=> x = ( -180 ) + 135

=> x = -45

b) ( 102 - 3x ) / 3 = -19

=> 102 - 3x = ( -19 ) * 3

=> 3x = 102 - ( -57 )

=> x = 159 / 3

=> x = 53

mình chỉ hướng dẫn bn từng bc nha

bn tính nhân chia trc cộng trừu sau

tính từ ngoặc tròn -> ngoặc vuông -> ngoặc nhọn

tíc mình nha

A={500-[100+(120-19x20:10+110)-140]+102}

A={500-[100+192-140]+102}

A={500-152+102}

A=450

Ax2:3=450x3:3=1350:3=450

a) 52x - 3 - 2 . 52 = 52 . 3

x - 3/52 - 2 = 3

x = 3 + 2 + 3/52

x = 263/52

b) 740 / (x + 10) = 102 - 2 . 13

740 / (x + 10) = 76

x + 10 = 740 / 76

x + 10 = 185/19

x = 185/19 - 10

x = -5/19

c) 65 - 4x + 2 = 20140

65 - 4x = 20140 - 2

65 - 4x = 20138

4x = 65 - 20138

4x = -20073

x = -20073/4

d) 120 + 2 . (3x - 17) = 214

60 + 3 . x - 17 = 107

20 + x - 17/3 = 107/3

20 + x = 107/3 + 17/3

20 + x = 124/3

x = 124/3 - 20

x = 64/3

e) 41 - 2x + 1 = 9

42 - 2x = 9

21 - x = 9/2

x = 21 - 9/2

x = 33/2

_{^{a, A = ( 2007 - 1969 )}}

_{^{= (2000 - 1969) + 7}}

_{^{= 31 + 7 = 38}}

_{^{b, 5689 - ( x - 2008 )}}

_{^{= 5989 - x + 2008}}

Có 1 vế sao tính??

_{^{c, 475 : 5 + 120 : 5 - 195 : 5}}

_{^{= (475 + 120 - 195):5}}

_{^{= 400:5=80}}

_{^{d, 432 : 6 - 234 : 6 + 102 : 6}}

_{^{= (432 + 102 - 234):6}}

= 300:6

=50

\(A=3^{101}+3^{102}+3^{103}+...+3^{200}\)

\(3A=3^{102}+3^{103}+3^{104}+...+3^{201}\)

\(3A-A=\left(3^{102}+3^{103}+3^{104}+3^{201}\right)-\left(3^{101}+3^{102}+3^{103}+...+3^{201}\right)\)

\(2A=3^{201}-3^{101}\)

\(2A=3^{100}\)

\(\Rightarrow A=3^{100}:2\)

\(A=3^{101}+3^{102}+3^{103}+...+3^{200}\)

\(A=3^{101}+3^{102}+3^{103}+3^{104}+...+3^{197}+3^{198}+3^{199}+3^{200}\)

\(A=3^{100}\left(3+3^2+3^3+3^4\right)+...+3^{196}\left(3+3^2+3^3+3^4\right)\)

\(A=120\left(3^{100}+...+3^{196}\right)⋮120\)

a: \(\frac{52}{17}>\frac{51}{17}=3\)

\(3=\frac{121}{41}>\frac{120}{41}\)

Do đó: \(\frac{52}{17}>\frac{120}{41}\)

b: \(\frac34+\frac14:\left(\frac{7}{12}-\frac16\right)\)

\(=\frac34+\frac14:\left(\frac{7}{12}-\frac{2}{12}\right)\)

\(=\frac34+\frac14:\frac{5}{12}\)

\(=\frac34+\frac14\times\frac{12}{5}=\frac34+\frac35=\frac{15}{20}+\frac{12}{20}=\frac{27}{20}\)

c: \(372,463\cdot998+744,926\)

\(=372,463\cdot998+372,463\cdot2\)

\(=372,463\times\left(998+2\right)=372,463\times1000=372463\)

d: Số số hạng trong dãy số 2;4;6;...;100 là:

\(\left(100-2\right):2+1=98:2+1=49+1=50\) (số)

\(2-4+6-8+10-12+\cdots+98-100+102\)

\(=\left(2-4\right)+\left(6-8\right)+\cdots+\left(98-100\right)+102\)

=(-2)+(-2)+...+(-2)+102

\(=-2\cdot\frac{50}{2}+102=-50+102=52\)

e: (y+112)-113=79

=>y+112-113=79

=>y-1=79

=>y=79+1=80

f: \(\frac34-y=\frac12\)

=>\(y=\frac34-\frac12=\frac14\)

g: \(\left(\frac45-2\times y\right)+\frac16=\frac56\)

=>\(\frac45-2\times y=\frac56-\frac16=\frac46=\frac23\)

=>\(2\times y=\frac45-\frac23=\frac{12}{15}-\frac{10}{15}=\frac{2}{15}\)

=>\(y=\frac{2}{15}:2=\frac{1}{15}\)

h: (y+1)+(y+2)+...+(y+50)=1750

=>50y+(1+2+...+50)=1750

=>\(50y+50\times\frac{51}{2}=1750\)

=>50y+1275=1750

=>50y=1750-1275=475

=>\(y=\frac{475}{50}=9,5\)

đúng hết rồi

Theo em, kết quả của Nam sai

120 = 2^3×3×5

102 = 2×3×17