34x+1 =27x+3
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a) \(12x^3+8x^2-3x-2=4x^2\left(3x+2\right)-\left(3x+2\right)\)
\(=\left(3x+2\right)\left(4x^2-1\right)=\left(3x+2\right)\left(2x-1\right)\left(2x+1\right)\)
b) \(18x^3+27x^2-2x-3=9x^2\left(2x+3\right)-\left(2x+3\right)\)
\(=\left(2x+3\right)\left(9x^2-1\right)=\left(2x+3\right)\left(3x-1\right)\left(3x+1\right)\)
c) \(8x^3+4x^2-34x+15=4x^2\left(2x-3\right)+8x\left(2x-3\right)-5\left(2x-3\right)\)
\(=\left(2x-3\right)\left(4x^2+8x-5\right)=\left(2x-3\right)\left(2x-1\right)\left(2x+5\right)\)
bài 1 : ta có : \(A=27x^3+27x^2y+9xy^2+y^3=\left(3x+y\right)^3\)
\(=\left(3.\left(-3\right)+5\right)^3=\left(-9+5\right)^3=\left(-4\right)^3=-64\)
bài 2 : a) ta có : \(12a^2-3ab+8ac-2bc=3a\left(4a-b\right)+2c\left(4a-b\right)\)
\(=\left(3a+2c\right)\left(4a-b\right)\) câu này mk sữa đề lại chút .
b) ta có : câu này đề sai rồi .
nếu phân tích ra nó sẽ thành : \(17x^2+34x-5=\left(17x+17-\sqrt{374}\right)\left(x+\dfrac{17+\sqrt{374}}{17}\right)\)
c) ta có : \(4x^4+81=\left(2x^2\right)^2+36x^2+81-36x^2\)
\(=\left(2x^2+9\right)^2-36x^2=\left(2x^2+9-6x\right)\left(2x^2+9+6x\right)\)
câu 3 : a) ta có : \(-3x^2+2x+1=0\Leftrightarrow-3x^2+3x-x+1=0\)
\(\Leftrightarrow-3x\left(x-1\right)-\left(x-1\right)=0\Leftrightarrow\left(-3x-1\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}-3x-1=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{3}\\x=1\end{matrix}\right.\) vậy \(x=\dfrac{-1}{3};x=1\)
b) ta có : \(x\left(x-3\right)=2x-6=x\left(x-3\right)-2\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x-2=0\\x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=3\end{matrix}\right.\)
vậy \(x=2;x=3\)
\(1-27x^3\)
\(=1-\left(3x\right)^3\)
\(=\left(1-3x\right)\left(1+3x+9x^2\right)\)
\(---\)
\(x-3^3+27\)
\(=x-27+27=x\)
\(---\)
\(27x^3+27x^2+9x+1\)
\(=\left(3x\right)^3+3\cdot\left(3x\right)^2\cdot1+3\cdot3x\cdot1^2+1^3\)
\(=\left(3x+1\right)^3\)
\(---\)
\(\dfrac{x^6}{27}-\dfrac{x^4y}{3}+x^2y^2-y^3\) (sửa đề)
\(=\left(\dfrac{x^2}{3}\right)^3-3\cdot\left(\dfrac{x^2}{3}\right)^2\cdot y+3\cdot\dfrac{x^2}{3}\cdot y^2-y^3\)
\(=\left(\dfrac{x^2}{3}-y\right)^3\)
#Ayumu
4x+1=3x+9 nên x = 9 - 1 = 8
Vậy x = 8
\(3^{4x+1}=27^{x+3}\)
\(\Rightarrow3^{4x+1}=3^{3\left(x+3\right)}\)
\(\Rightarrow4x+1=3\left(x+3\right)\)
\(\Rightarrow4x-3x=9+1\)
\(\Rightarrow x=10\)