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x3 + 7x - 6
= x3 - x - 6x - 6
= x3 - x - 6 (x+1)
= x (x2 - 1) - 6 (x+1)
= (x + 1) ( x (x - 1) - 6 )
= ( x + 1) ((x2 - x - 6))
= (x + 1) ((x2 + 2 - 3 - 6))
= (x + 1) (x(x +2) - 3 ( x + 2))
= (x + 1)(x + 2)(x + 3)
\(5-7x^2=\left(\sqrt{5}\right)^2-\left(x\sqrt{7}\right)^2\)
\(=\left(\sqrt{5}-x\sqrt{7}\right)\left(\sqrt{5}+x\sqrt{7}\right)\)
\(3+4x=\left(\sqrt{3}\right)^2-\left(2\sqrt{x}\right)^2\) ( do x<0 )
\(=\left(\sqrt{3}-2\sqrt{x}\right)\left(3+2\sqrt{x}\right)\)
xét \(x\ne0\)ta có :
\(M=\)\(^{x^2\cdot\left(x^2+6x+7-\frac{6}{x}+\frac{1}{x^2}\right)}\)
Đặt \(x-\frac{1}{x}=t\Rightarrow t^2=x^2-2+\frac{1}{x^2}\Leftrightarrow t^2+2=x^2+\frac{1}{x^2}\)
Do đó \(M=x^2\cdot\left(t^2+2+6t+7\right)\Leftrightarrow x^2\cdot\left(t^2+6t+9\right)\)
\(\Leftrightarrow M=x^2\cdot\left(t+3\right)^2\)
M=\(x^4+3x^3-x^2+3x^3+9x^2-3x-x^2-3x+1\)
\(=x^2(x^2+3x-1)+3x\left(x^2+3x-1\right)-\left(x^2+3x-1\right)\)
\(=\left(x^2+3x-1\right)^2\)
Ta có: \(P\left(x\right)=x^4+6x^3+7x^2-6x+1\)
\(=x^4+\left(6x^3-2x^2\right)+\left(9x^2-6x+1\right)\)
\(=x^4+2x^2\left(3x-1\right)+\left(3x-1\right)^2\)
\(=\left(x^2+3x-1\right)^2\)
4x^2 - 7x -2 = 4x^2 - 8x + x - 2 = 4x(x - 2) + (x - 2) = (x -2)(4x + 1)
\(x-6\sqrt{x-3}+6\text{=}x-3-6\sqrt{x-3}+9\)
\(\text{=}\left(\sqrt{x-3}\right)^2-2.3.\sqrt{x-3}+\left(3\right)^2\)
\(\text{=}\left(\sqrt{x-3}-3\right)^2\)
A = \(x-6\)\(\sqrt{x-3}\) + 6 (đkxd \(x>3\))
A = (\(x\) - 3) - 2.3.\(\sqrt{x-3}\) + 9
A = (\(\sqrt{x-3}\))2 - 2.3.\(\sqrt{x-3}\) + 32
A = (\(\sqrt{x-3}\)- 3)2
Lời giải:
$x-5\sqrt{x}+6=x-2\sqrt{x}-3\sqrt{x}+6$
$=\sqrt{x}(\sqrt{x}-2)-3(\sqrt{x}-2)$
$=(\sqrt{x}-2)(\sqrt{x}-3)$