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#) TL :
x8 + x4 + 1
= (x4)2 + 2x4 + 1 - x4
= ( x4 + 1 )2 - x4
= ( x4 - x2 + 1 )(x4 + x2 + 1)
= ( x4 - x2 + 1)( x2 - x + 1)( x2 + x + 1 )
Chúc bn hok tốt ạ :3
\(=x^4-16x^2+100=x^4+20x^2+100-36x^2\)
\(=\left(x^2+10\right)^2-\left(6x\right)^2=\left(x^2-6x+10\right)\left(x^2+6x+10\right)\)
\(\left(x^2-8\right)^2+36\)
\(=x^4-16x^2+64+36\)
\(=x^4-16x^2+100\)
\(=x^4+20x^2+100-36x^2\)
\(=\left(x^2+10\right)^2-\left(6x\right)^2\)
\(=\left(x^2-6x+10\right)\left(x^2+6x+10\right)\)
Sửa đề: \(x^4+x^2+1\)
\(=x^4+2x^2+1-x^2\)
\(=\left(x^2+1\right)^2-x^2\)
\(=\left(x^2+x+1\right)\left(x^2-x+1\right)\)
\(a^8+a^4+1=\left(a^8+2a^4+1\right)-a^4\)
\(=\left(a^4+1\right)^2-a^4\)
\(=\left(a^4-a^2+1\right)\left(a^4+a^2+1\right)\)
\(=\left[\left(a^4-2a^2+1\right)-a^2\right]\left(a^4+a^2+1\right)\)
\(=\left[\left(a^2-1\right)^2-a^2\right]\left(a^4+a^2+1\right)\)
\(=\left(a^2-a-1\right)\left(a^2-a+1\right)\left(a^4+a^2+1\right)\)
*\(a^8+a^7+1=a^8+a^7+a^6-a^6+a^5-a^5+a^4-a^4+a^3-a^3+a^2-a^2+a-a+1\)\(=\left(a^8+a^7+a^6\right)+\left(a^5+a^4+a^3\right)+\left(a^2+a+1\right)-\left(a^6+a^5+a^4\right)-\left(a^3+a^2+a\right)\)\(=a^6\left(a^2+a+1\right)+a^3\left(a^2+a+1\right)+\left(a^2+a+1\right)-a^4\left(a^2+a+1\right)-a\left(a^2+a+1\right)\)\(=\left(a^2+a+1\right)\left(a^6-a^4+a^3-a+1\right)\)
Bài này ko thể phân tích theo kiểu lớp 8 được (chưa học căn thức)
\(2x^2-6x+1=\left(\sqrt{2}x\right)^2-2.\sqrt{2}x.\frac{3\sqrt{2}}{2}+\left(\frac{3\sqrt{2}}{2}\right)^2-\frac{7}{2}\)
\(=\left(\sqrt{2}x-\frac{3\sqrt{2}}{2}\right)^2-\left(\frac{\sqrt{14}}{2}\right)^2\)
\(=\left(\sqrt{2}x-\frac{3\sqrt{2}}{2}+\frac{\sqrt{14}}{2}\right)\left(\sqrt{2}x-\frac{3\sqrt{2}}{2}-\frac{\sqrt{14}}{2}\right)\)
\(=\left(\sqrt{2}x+\frac{\sqrt{14}-3\sqrt{2}}{2}\right)\left(\sqrt{2}x-\frac{\sqrt{14}+3\sqrt{2}}{2}\right)\)
\(2x^2-6x+1=2\left(x^2-3x+\frac{9}{4}-\frac{7}{4}\right)=2\left[\left(x-\frac{3}{2}\right)^2-\left(\frac{\sqrt{7}}{2}\right)^2\right]=2\left(x-\frac{3}{2}-\frac{\sqrt{7}}{2}\right)\left(x-\frac{3}{2}+\frac{\sqrt{7}}{2}\right)\)
\(=2\left(x-\frac{3+\sqrt{7}}{2}\right)\left(x-\frac{3-\sqrt{7}}{2}\right)\)
\(x^8-1=x^8-x^4+x^4-1\)
\(=x^4\left(x^2-1\right)+\left(x^4-1\right)\)
\(=x^4\left(x^2-1\right)+\left(x^2-1\right)\left(x^2+1\right)\)
\(=\left(x^2-1\right)\left(x^4+x^2+1\right)\)
\(=\left(x-1\right)\left(x+1\right)\left(x^4+x^2+1\right)\)
\(x^8-1\)
\(=\left(x^4\right)^2-1^2\)
\(=\left(x^4-1\right)\left(x^4+1\right)\)
\(=\left(x^2-1\right)\left(x^2+1\right)\left(x^4+1\right)\)
\(=\left(x-1\right)\left(x+1\right)\left(x^2+1\right)\left(x^4+1\right)\)