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a) \(x^2-2x-15\)
\(\Leftrightarrow x^2-2x+1-16\)
\(\Leftrightarrow\left(x-1\right)^2-4^2\)
\(\Leftrightarrow\left(x-5\right)\left(x-3\right)\)
\(a,x^2-2x-15=\left(x^2-2x+1\right)-16.\)
\(=\left(x-1\right)^2-4^2\)
\(=\left(x-5\right)\left(x+3\right)\)
\(x\sqrt{x}-3x+4\sqrt{x}-2=x\sqrt{x}-x-2x+2\sqrt{x}+2\sqrt{x}-2\)
\(=x\left(\sqrt{x}-1\right)-2\sqrt{x}\left(\sqrt{x}-1\right)+2\left(\sqrt{x}-1\right)\)
\(=\left(\sqrt{x}-1\right)\left(x-2\sqrt{x}+2\right)\)
x4-25x2+26x-4
= (x4-25x2)+ (26x-4)
= ((x2)2-(5x)2)+ 2(13x-2)
= (x2-5x)(x2+5x)
Lời giải:
$x\sqrt{x}-3x+4\sqrt{x}-2=(x\sqrt{x}-x)-(2x-2\sqrt{x})+(2\sqrt{x}-2)$
$=x(\sqrt{x}-1)+2\sqrt{x}(\sqrt{x}-1)+2(\sqrt{x}-1)$
$=(\sqrt{x}-1)(x+2\sqrt{x}+2)$
\(x^2-2xy+5x-10y\)
\(=x\left(x-2y\right)+5\left(x-2y\right)\)
\(=\left(x+5\right)\left(x-2y\right)\)
\(x^2-2xy+5x-10y\)
\(=\left(x^2-2xy\right)+\left(5x-10y\right)\)
\(=x\left(x-2y\right)+5\left(x-2y\right)\)
\(=\left(x-2y\right)\left(x+5\right)\)
\(x-3\sqrt{x}+\sqrt{xy}-3y\)
\(=\left(x-3\sqrt{x}\right)+\left(\sqrt{xy}-3y\right)\)
\(=\sqrt{x}\left(\sqrt{x}-3\right)+y\left(\sqrt{x}-3\right)\)
\(=\left(\sqrt{x}-3\right)\left(\sqrt{x}+y\right)\)
= (x^4-4x^3)+(3x^3-12x^2)+(2x^2-8x)-(2x-8)
= x^3.(x-4)+3x^2.(x-4)+2x.(x-4)-2.(x-4)
= (x-4).(x^3+3x^2+2x-2)
Tk mk nha
\(-25x^2\sqrt{2}+10x+4\sqrt{2}=-\sqrt{2}\left(25x^2-\dfrac{10}{\sqrt{2}}-4\right)=-\sqrt{2}.\left(\left(25x\right)^2-2.5.\dfrac{1}{\sqrt{2}}+\dfrac{1}{2}-\dfrac{5}{2}\right)=-\sqrt{2}\left[\left(5x-\dfrac{1}{\sqrt{2}}\right)^2-\dfrac{5}{2}\right]=-\sqrt{2}.\left(5x-\dfrac{1}{\sqrt{2}}-\dfrac{\sqrt{5}}{\sqrt{2}}\right).\left(5x-\dfrac{1}{\sqrt{2}}+\dfrac{\sqrt{5}}{\sqrt{2}}\right)=-\sqrt{2}.\left(5x-\dfrac{1+\sqrt{5}}{\sqrt{2}}\right)\left(5x-\dfrac{1-\sqrt{5}}{\sqrt{2}}\right)\)