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,(8x-3).(3x+2)-(4x+7).(x+4)=(2x+1).(5x-1)-33 đúng không bạn

`#3107.101107`

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

`<=> x(x^2 - 25) - (x^3 + 2^3) = 5`

`<=> x^3 - 25x - x^3 - 8 = 5`

`<=> -25x - 8 = 5`

`<=> -25x = 13`

`<=> x = -13/25`

Vậy, `x = -13/25`

_____

\((x+1)^3 - (x-1)^3 -6(x-1)^2 = -19\)

`<=> x^3 + 3x^2 + 3x + 1 - (x^3 - 3x^2 + 3x - 1) - 6(x^2 - 2x + 1) = -19`

`<=> x^3 + 3x^2 + 3x + 1 - x^3 + 3x^2 - 3x + 1 - 6x^2 + 12x - 6 = -19`

`<=> (x^3 - x^3) + (3x^2 + 3x^2 - 6x^2) + (3x - 3x + 12x) + (1 + 1 - 6) = -19`

`<=> 12x - 4 = -19`

`<=> 12x = -15`

`<=> x = -15/12 = -5/4`

Vậy, `x = -5/4.`

________

`@` Sử dụng các hđt:

`1)` `A^2 + B^2 = (A - B)(A + B)`

`2)` `A^3 + B^3 = (A + B)(A^2 - AB + B^2)`

`3)` `(A - B)^3 = A^3 - 3A^2B + 3AB^2 - B^3`

`4)` `(A + B)^3 = A^3 + 3A^2B + 3AB^2 + B^3`

`5)` `(A - B)^2 = A^2 - 2AB + B^2.`

a: \(x\left(x+5\right)\left(x-5\right)-\left(x+2\right)\left(x^2-2x+4\right)=5\)

=>\(x\left(x^2-25\right)-x^3-8=5\)

=>\(x^3-25x-x^3-8=5\)

=>-25x=13

=>\(x=-\dfrac{13}{25}\)

b: \(\left(x+1\right)^3-\left(x-1\right)^3-6\left(x-1\right)^2=-19\)

=>\(x^3+3x^2+3x+1-x^3+3x^2-3x+1-6\left(x^2-2x+1\right)=-19\)

=>\(6x^2+2-6x^2+12x-6=-19\)

=>12x-4=-19

=>12x=-15

=>x=-5/4

a) /x+\(\frac{4}{15}\)/ - / -3,75/ = -2,15

=> \(\orbr{\begin{cases}x+\frac{4}{15}+3,75=-2,15\\x+\frac{4}{15}+3,75=2,15\end{cases}}\)

=> ....v.....v giải ra ( từng th )

bài khác tương tự

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chi can lam bai c,d,e la duoc

nhung bai con lai mik tu lam duoc

\(2-\left|\dfrac{3}{2}x-\dfrac{1}{4}\right|=\left|-\dfrac{5}{4}\right|\)

\(\Rightarrow2-\left|\dfrac{3}{2}x-\dfrac{1}{4}\right|=\dfrac{5}{4}\)

\(\Rightarrow\left|\dfrac{3}{2}x-\dfrac{1}{4}\right|=2-\dfrac{5}{4}\)

\(\Rightarrow\left|\dfrac{3}{2}x-\dfrac{1}{4}\right|=\dfrac{3}{4}\)

\(\Rightarrow\left[{}\begin{matrix}\dfrac{3}{2}x-\dfrac{1}{4}=\dfrac{3}{4}\Rightarrow\dfrac{3}{2}x=1\Rightarrow x=\dfrac{2}{3}\\\dfrac{3}{2}x-\dfrac{1}{4}=-\dfrac{3}{4}\Rightarrow\dfrac{3}{2}x=-\dfrac{1}{2}\Rightarrow x=-\dfrac{1}{3}\end{matrix}\right.\)

a/ 3(1 - x) - 5(2x - 2) = 0 

    => 3 - 3x - 10x + 10 = 0

    => -13x = -13

    => x = 1

     Vậy x = 1

b/ |3x - 2| - 4 = 0 => |3x - 2| = 4  

    Suy ra 2 trường hợp:

    Vậy x = 2 , x = -2/3

c/ 2x - x³ = 0 => x.(2 - x²) = 0 

     => x = 0 

    hoặc 2 - x² = 0 => x² = 2 => x = \(\sqrt{2}\)  hoặc x = \(-\sqrt{2}\)

         Vậy \(x=\left\{0;\sqrt{2};-\sqrt{2}\right\}\)

d/ x(1 - 2x) + (2x² - x + 4) = 0 

     => x - 2x² + 2x² - x + 4 = 0

     => 4 = 0 (vô lí)

     Vậy vô nghiệm