sai rồi: (x⁴ + x²) - (9x³ + 9x)

= x²(x² + 1) - 9x(x² + 1)

= (x² - 9x)(x² + 1)

mày viết lại cái đề bài hộ tao cái

a: \(\Leftrightarrow\left(x+3\right)\left(x^2-3x+9\right)+9x\left(x+3\right)=0\)

=>(x+3)(x^2+6x+9)=0

=>x=-3

b: \(\Leftrightarrow x^2-2x-x^3+6x^2-4=0\)

=>-x^3+6x^2-2x-4=0

hay \(x\in\left\{5.5;1.14;-0.64\right\}\)

c: =>(3x-1)^3=8

=>3x-1=2

=>3x=3

=>x=1

đề

Xin lỗi các bạn hơi khó hiểu đề đây là phân số

(x-1)*x^2*(x^3+x^2-9)

x⁴(x² - 1) - 9x²(x - 1)

=x⁴(x - 1)(x + 1) - 9x²(x -1)

=(x - 1)(x⁵ + x⁴ - 9x²)

\(x^6-x^4-9x^3+9x^2\)

\(=x^6-x^5+x^5-x^4-9x^2\left(x-1\right)\)

\(=x^5\left(x-1\right)+x^4\left(x-1\right)-9x^2\left(x-1\right)\)

\(=\left(x-1\right)\left(x^5+x^4-9x^2\right)\)

\(x^6-x^4-9x^3+9x^2\)

\(=x^4.\left(x^2-1\right)-9x^2\left(x-1\right)\)

\(=x^4.\left(x-1\right)\left(x+1\right)-9x^2\left(x-1\right)\)

\(=\left(x-1\right)\left[x^4.\left(x+1\right)-9x^2\right]\)

a) \(x^3-7x+6=x^3+3x^2-x^2-3x-2x^2-6x+2x+6\)

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

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

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

=\(\left\{\begin{matrix}x+3=0=>x=-3\\x-2=0=x=2\\x-1=0=>x=1\end{matrix}\right.\)

\(b...x^3-19x+30=0\)

\(=>x^3+5x^2-2x^2-10x-3x^2-15x+6x+30=0\)

=>\(x^2\left(x+5\right)-2x\left(x+5\right)-3x\left(x+5\right)+6\left(x+5\right)=0\)

=>\(\left(x+5\right)\left(x^2-2x-3x+6\right)=0\)

=>\(\left(x+5\right)\left(x-3\right)\left(x-2\right)=0\)

=>\(\left\{\begin{matrix}x-3=0=>x=3\\x-2=0=>x=2\\x+5=0=>x=-5\end{matrix}\right.\)

Vậy x=-5;2;3

câu d nè bạn

\(x^3+9x^2+23x+15=x^3+5x^2+4x^2+20x+3x+15\)

=\(x^2\left(x+5\right)+4x\left(x+5\right)+3\left(x+5\right)\)

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

câu c nè

\(x^3-6x^2-x+30=\left(x^3-5x^2\right)-\left(x^2-5x\right)-\left(6x-30\right)\)

\(=x^2\left(x-5\right)-x\left(x-5\right)-6\left(x-5\right)=\left(x^2-x-6\right)\left(x-5\right)\)

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

tick rui minh làm tiếp cho