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= (x2 + 1)(x+1)2 + x2 + 1 -1 = (x2 + 1) [(x+1)2 + 1] - 1 = (x2 + 1) (x2 + 1 + 2x + 1) - 1 = (x2 + 1)2 + 2x(x2 + 1) + x2 + 1 - 1
= (x2 + 1)2 + 2x(x2 + 1) + x2 = (x2 + 1 + x)2
Đặt x^2 + x + x = t
Ta có BT : \(t\left(t+1\right)-1^2=t^2+t-1\):)) đề lỗi j ko ?
Ta có:\(3\left(x^4+x^2+1\right)-\left(x^2+x+1\right)^2=3x^4+3x^2+3-x^4-x^2-1-2x^3-2x-2x^2\)
\(=2x^4-2x^3-2x+2=2x^3\left(x-1\right)-2\left(x-1\right)=2\left(x^3-1\right)\left(x-1\right)\)
\(=2\left(x-1\right)^2\left(x^2+x+1\right)\)
\(3\left(x^4+x^2+1\right)-\left(x^2+x+1\right)^2\)
\(=3\left(x^4+x^2+1\right)-\left(x^4+x^2+1+2x^3+2x^2+2x\right)\)
\(=\left(x^4+x^2+1\right)\left(3-2x^3-2x^2-2x\right)\)
\(3\left(x^4+x^2+1\right)-\left(x^2+x+1\right)^2\)
\(=3\left(x^2+x+1\right)\left(x+x^2+x+1\right)\)
\(=3\left(x^2+x+1\right)\left(x^2+2x+1\right)\)
\(=3\left(x^2+x+1\right)\left(x+1\right)^2\)
Em sửa lại tên đi nhé!
\(\left(x^2-1\right)^2-x\left(x^2-1\right)-2x^2\)
= \(\left(x^2-1\right)^2-2.\left(x^2-1\right).\frac{x}{2}+\frac{x^2}{4}-\frac{x^2}{4}-2x^2\)
= \(\left(x^2-1-\frac{x}{2}\right)^2-\frac{9}{4}x^2\)
\(=\left(x^2-1-\frac{x}{2}-\frac{3}{2}x\right)\left(x^2-1-\frac{x}{2}+\frac{3}{2}x\right)\)
= \(\left(x^2-2x-1\right)\left(x^2-x-1\right)\)
Phân tích tiếp được đấy:
\(x^2-2x-1=\left(x-1\right)^2-2=\left(x-1-\sqrt{2}\right)\left(x-1+\sqrt{2}\right)\)
\(x^2-x-1=\left(x-\frac{1}{2}\right)^2-\frac{5}{4}=\left(x-\frac{1}{2}-\frac{\sqrt{5}}{2}\right)\left(x-\frac{1}{2}+\frac{\sqrt{5}}{2}\right)\)
Thay vào nhé!
\(x^2\left(x+1\right)^2+x^2+\left(x+1\right)^2\)
\(=\left(x^2+1\right)\left(x+1\right)^2+x^2+1-1\)
\(=\left(x^2+1\right)\left[\left(x+1\right)^2+1\right]-1\)
\(=\left(x^2+1\right)\left(x^2+1+2x+1\right)-1\)
\(=\left(x^2+1\right)^2+2x\left(x^2+1\right)+x^2+1-1\)
\(=\left(x^2+1\right)^2+2x\left(x^2+1\right)+x^2\)
\(=\left(x^2+1+x\right)^2\)