\(\Leftrightarrow-\dfrac{2}{5}\left(4x-3\right)^2=-\dfrac{5}{18}\)

\(\Leftrightarrow\left(4x-3\right)^2=\dfrac{25}{36}\)

\(\Leftrightarrow4x-3\in\left\{\dfrac{5}{6};-\dfrac{5}{6}\right\}\)

hay \(x\in\left\{\dfrac{23}{24};\dfrac{13}{24}\right\}\)

b: \(47x+52x+x=4.75\)

\(\Leftrightarrow100x=300\)

hay x=3

( 4x + 5 ) : 3 - 121 : 11 = 4

( 4x + 5 ) : 3 - 11 = 4

( 4x + 5 ) : 3 = 4 + 11

( 4x + 5 ) : 3 = 15

4x + 5 = 15 x 3

4x + 5 = 45

4x = 45 - 5

4x = 40

x = 40 : 4

x = 10

( 4x + 5) : 3 - 12 : 11 = 4

( 4x + 5) : 3 - 12 = 4 x 11 = 44

( 4x + 5) : 3 = 44 + 12 = 56

4x + 5 = 56 x 3 = 168

4x = 168 - 5 = 163

x = 163 : 4

x = ....

< Đề sai thì phải >

\(\left(4x+5\right):3-12:11=4\)

\(\left(4x+5\right):3-12:11=4+\frac{12}{11}\)

\(\left(4x+5\right):3=\frac{56}{11}\)

\(\left(4x+5\right):3=\frac{56}{11}\cdot3\)

\(4x+5=\frac{168}{11}\)

\(4x=\frac{168}{11}-5\)

\(4x=\frac{113}{11}\)

\(x=\frac{113}{11}:4\)

\(x=\frac{113}{44}\)

a) x²³= 64 . x²⁰

x²³: x²⁰= 64

x³= 64

=> x³= 4³

=> x =4

Vậy...

a)\(x^{23}=64.x^{20}\)

\(\Leftrightarrow\frac{x^{23}}{x^{20}}=64\)

\(\Leftrightarrow x^3=64\Rightarrow x=4\)

b)\(\left(4x-3\right)^4=3-4x\)

\(\Leftrightarrow\left(3-4x\right)^4=3-4x\)

\(\Leftrightarrow\left(3-4x\right)^3=1\)

\(\Leftrightarrow3-4x=1\)

\(\Leftrightarrow x=\frac{1}{2}\)

\(\dfrac{3x-4}{4}=\dfrac{4x-8}{5}\)

\(\Leftrightarrow\dfrac{3x-4}{4}-\dfrac{4x-8}{5}=0\)

\(\Leftrightarrow\dfrac{5\left(3x-4\right)}{20}-\dfrac{4\left(4x-8\right)}{20}=0\)

\(\Leftrightarrow\dfrac{15x-20}{20}-\dfrac{16x-32}{20}=0\)

\(\Leftrightarrow\dfrac{15x-20-16x+32}{20}=0\)

\(\Leftrightarrow\dfrac{x-12}{20}=0\)

\(\Leftrightarrow x-12=0\)

\(\Leftrightarrow x=12\)

gọi số cn đội 1;2;3 là x;y;z theo bài ra ta có:

2x/3 = 8y/11 = 4z/5

y+z -x = 18

theo t/c của tỷ lệ thức ta tìm dc x;y;z

( đến đây ai cũng làm dc rùi)

(copy á,mak kệ đi)

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= -1 - (2-3-4+5) - (6+7+8-9) -... - (198 -199-120+121)

A= -1 - 0-0-...-0

A= -1

nhớ k giùm mk

thanks bạn

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