Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Lười làm quá. Chơi phân tích nhân tử luôn
Ta có: \(x^3+3x^2+3x+2=-\sqrt[3]{x^3-8x-8}\)
\(\Leftrightarrow\left(x^3+3x^2+3x+2\right)^3=\left(-\sqrt[3]{x^3-8x-8}\right)^3\)
\(\Leftrightarrow x^9+9x^8+36x^7+87x^6+144x^5+171x^4+148x^3+90x^2+28x=0\)
\(\Leftrightarrow x\left(x+1\right)\left(x+2\right)\left(x^6+6x^5+16x^4+27x^3+31x^2+24x+14\right)=0\)
\(\Leftrightarrow\hept{\begin{cases}x=0\\x=-1\\x=-2\end{cases}}\)
b)\(3x^3+6x^2-75x-150=0\Leftrightarrow3\left(x^3+2x^2-25x-50\right)=0\Leftrightarrow x^3+2x^2-25x-50=0\)
<=>\(x^2\left(x+2\right)-25\left(x+2\right)=0\Leftrightarrow\left(x^2-25\right)\left(x+2\right)=0\Leftrightarrow\left(x-5\right)\left(x+5\right)\left(x+2\right)=0\)
<=>x-5=0 hoặc x+5=0 hoặc x+2=0<=>x=5 hoặc x=-5 hoặc x=-2
c)\(2x^5-3x^4+6x^3-8x^2+3=0\Leftrightarrow2x^5+x^4-4x^4-2x^3+8x^3+4x^2-12x^2+3=0\)
<=>\(x^4\left(2x+1\right)-2x^3\left(2x+1\right)+4x^2\left(2x+1\right)-3\left(4x^2-1\right)=0\)
<=>\(x^4\left(2x+1\right)-2x^3\left(2x+1\right)+4x^2\left(2x+1\right)-3\left(2x-1\right)\left(2x+1\right)=0\)
<=>\(\left(2x+1\right)\left(x^4-2x^3+4x^2-6x+3\right)=0\)
<=>\(\left(2x+1\right)\left(x^4-2x^3+x^2+3x^2-6x+3\right)=0\)
<=>\(\left(2x+1\right)\left[x^2\left(x^2-2x+1\right)+3\left(x^2-2x+1\right)\right]=0\)
<=>\(\left(2x+1\right)\left(x^2+3\right)\left(x^2-2x+1\right)=0\Leftrightarrow\left(2x+1\right)\left(x^2+3\right)\left(x-1\right)^2=0\)
Vì \(x^2\ge0\Rightarrow x^2+3\ge3>0\Rightarrow\orbr{\begin{cases}2x+1=0\\\left(x-1\right)^2=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=-\frac{1}{2}\\x=1\end{cases}}\)
a) 2x3 - x2 - 8x + 4 = 0
x2.(2x - 1) - 4.(2x - 1) = 0
(x2 - 4)(2x - 1) = 0
\(\Rightarrow\orbr{\begin{cases}x^2-4=0\\2x-1=0\end{cases}}\Rightarrow\orbr{\begin{cases}x^2=4\\x=\frac{1}{2}\end{cases}}\)
Với x2 = 4
=> x = 2 hoặc x = -2
=> x = {-2 ; 2 ; \(\frac{1}{2}\))
câu a:
\(8x^2-6x+3-2x=\left(2x-1\right)\sqrt{8x^2-6x+3}\)
đặt \(t=\sqrt{8x^2-6x+3}\Leftrightarrow t^2=8x^2-6x+3\)phương trình trở thành
\(t^2-2x=\left(2x-1\right)t\Leftrightarrow t^2-\left(2x-1\right)t-2x=0\)
có \(\Delta=\left(2x-1\right)^2+8x=\left(2x+1\right)^2\Rightarrow\orbr{\begin{cases}t=-1\\t=2x\end{cases}}\)
- \(t=-1\Rightarrow8x^2-6x+3=1\Leftrightarrow8x^2-6x+2=0VN\)
- \(t=2x\Rightarrow8x^2-6x+3=4x^2\Leftrightarrow4x^2-6x+3=0VN\)
Câu b:
Đặt \(t=\sqrt{x^2+1}\Leftrightarrow t^2=x^2+1\left(t>0\right)\)
PT\(\Leftrightarrow t^2-\left(x+3\right)t+3x=0\)
có :\(\Delta=\left(x+3\right)^2-4.3x=\left(x-3\right)^2\Rightarrow\orbr{\begin{cases}t=3\\t=x\end{cases}}\)
- \(t=3\Rightarrow9=x^2+1\Leftrightarrow x^2=8\Leftrightarrow\orbr{\begin{cases}x=2\sqrt{2}\\x=-2\sqrt{2}\end{cases}}\)
- \(t=x\Leftrightarrow x^2=x^2+1VN\)
x=-1
\(x^3+3x^2+3x+2+\sqrt[3]{x^3-8x-8}=0\Leftrightarrow x^3+3x^2+3x+2+x-\sqrt[3]{8x}-2=0\)\(\Leftrightarrow x^3+3x^2+4x-2\sqrt[3]{x}=0\Leftrightarrow\left(x^3+2x^2\right)+\left(x^2+2x\right)+2x-2\sqrt[3]{x}\)\(\Leftrightarrow x^2\left(x+2\right)+x\left(x+2\right)+2\left(x-\sqrt[3]{x}\right)\Leftrightarrow x\left(x+1\right)\left(x+2\right)+2\left(x-\sqrt[3]{x}\right)\)\(\Rightarrow|^{x\left(x+1\right)\left(x+2\right)=0\Rightarrow x=0;x+1=0\Leftrightarrow x=-1;x+2=0\Leftrightarrow x=-2}_{2\left(x-\sqrt[3]{x}\right)=0\Leftrightarrow x-\sqrt[3]{x}=0\Leftrightarrow x^3-x=0\Leftrightarrow x\left(x^2-1\right)=0\Leftrightarrow|^{x=0}_{x^2-1=0\Leftrightarrow x=\pm1}}\)
Vậy tập nghiệm của PT là S={0;-1;-2}