Chịu

a, (x + 2)(x² - 2x + 4 ) - x(x + 3)(x - 3) = 26

<=> x³ + 8 - x(x² - 9) = 26

<=> x³ + 8 - x³ + 9x = 26

<=> 9x - 18 = 0

<=> 9x = 18

<=> x = 2
b, (x - 3)(x² + 3x + 9) - x(x - 4)(x + 4) = 21

<=> x³ - 27 - x(x² - 16) = 21

<=> x³ - 27 - x³ + 16x = 21

<=> 16x - 48 = 0

<=> 16x = 48

<=> x = 3
c, (2x - 1)(4x² + 2x + 1) - 4x(2x² - 3) = 23

<=> 8x³ - 1 - 8x³ + 12x = 23

<=> 12x - 24 = 0

<=> 12x = 24

<=> x = 2

a/\(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x+3\right)\left(x-3\right)=26\)

↔ \(x^3+2^3\)\(-x\left(x^2-3^2\right)\)= 26

↔\(x^3+8-x^3+9x=26\)

↔\(9x=18\leftrightarrow x=2\)

Vậy x=2

b/\(\left(x-3\right)\left(x^2+3x+9\right)-x\left(x-4\right)\left(x+4\right)=21\)

\(\Leftrightarrow x^3-3^3-x\left(x^2-4^2\right)=21\)

\(\Leftrightarrow x^3-9-x^3+16x=21\)

\(\Leftrightarrow16x=30\)

\(\Leftrightarrow x=\frac{15}{8}\)

Vậy \(x=\frac{15}{8}\)

c/\(\left(2x-1\right)\left(4x^2+2x+1\right)-4x\left(2x^2-3\right)=23\)

↔\(\left(2x\right)^3-1^3-4x\left(2x^2-3\right)=23\)

↔\(8x^3-1-8x^3+12x=23\)

↔\(12x=24\leftrightarrow x=2\)

Vậy x=2

g)\(2907\left(2x+1\right)=8721\)

⇔\(2x+1=3\)

⇔\(2x=2\)

⇔\(x=1\)

h)\(\left(4x-16\right):1905=60\)

⇔\(4x-16=114300\)

⇔\(4x=114316\)

⇔\(x=28579\)

i)\(23+3x=5^6:5^3\)

⇔\(23+3x=5^3\)

⇔\(23+3x=125\)

⇔\(3x=102\)

⇔\(x=34\)

k)\(219-7\left(x+1\right)=100\)

⇔\(7\left(x+1\right)=119\)

⇔\(x+1=17\)

⇔\(x=16\)

a)5x-(4-2x+x²)(x+2)+x(x+1)=0

<=>5x-(4x+8-2x²-4x+x³+2x²)+x²+x=0

<=>5x-4x-8+2x²+4x-x³-2x²+x²+x=0

<=>-x³+x²+6x-8=0

<=>-x³+2x²-x²+2x+4x-8=0

<=>(x-2)(-x²-x+4)=0

<=>x-2=0 hoặc -x²-x+4=0

*x-2=0<=>x=2

* -x²-x+4=-x²-x-\(\frac{1}{4}\)+\(\frac{17}{4}\)=-(x+\(\frac{1}{2}\))²+\(\frac{17}{4}\)=0  <=>(x+\(\frac{1}{2}\))²=\(\frac{17}{4}\) <=>x thuộc tập hợp {\(\frac{\sqrt{17}}{2}\)-\(\frac{1}{2}\) ;-\(\frac{\sqrt{17}}{2}\)-\(\frac{1}{2}\)}

    vậy..................

   b)(4x²+2x+1)(2x-1)-4x(2x²-3)=23

   <=>8x³-4x²+4x²-2x+2x-1-(8x³-12x)=23

    <=>8x³-1-8x³+12x=23

     <=>12x=24

     <=>x=2

     Vậy..........

  Mấy bài này cậu chịu khó nháp tí là làm được thôi mà , chúc cậu thành công

Câu b :

\(\left(4x^2+2x+1\right)\left(2x-1\right)-4x\left(2x^2-3\right)=23\)

\(\Leftrightarrow8x^3-1-8x^3+12x-23=0\)

\(\Leftrightarrow12x-24=0\)

\(\Rightarrow x=2\)

Chọn A

Chọn A.

Do 2^x + 2^-x  > 0

Nên 

g: =>3x-10=200

hay x=70

c) (7x + x – 28) :100 – 38 = 9

<=> 8x - 28 = 4700

<=> x = 591