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a) Sửa đề :
\(x^4=a^4+4a^3b+6a^2b^2+4ab^3+b^4\)
\(x^4=\left(a^4+3a^3b+3a^2b^2+ab^3\right)+\left(a^3b+3a^2b^2+3ab^3+b^4\right)\)
\(x^4=a\left(a^3+3a^2b+3ab^2+b^3\right)+b\left(a^3+3a^2b+3ab^2+b^3\right)\)
\(x^4=\left(a+b\right)\left(a^3+3a^2b+3ab^2+b^3\right)\)
\(x^4=\left(a+b\right)\left[\left(a^3+2a^2b+ab^2\right)+\left(a^2b+2ab^2+b^3\right)\right]\)
\(x^4=\left(a+b\right)\left[a\left(a^2+2ab+b^2\right)+b\left(a^2+2ab+b^2\right)\right]\)
\(x^4=\left(a+b\right)^2\left(a+2ab+b^2\right)\)
\(x^4=\left(a+b\right)^4\)
b) Sửa đề:
\(x^5=a^5+5a^4b+10a^3b^2+10a^2b^3+5ab^4+b^5\)
\(x^5=\left(a^5+4a^4b+6a^3b^2+4a^2b^3+ab^4\right)+\left(a^4b+4a^3b^2+6a^2b+4ab^4+b^5\right)\)
\(x^5=a\left(a^4+4a^3b+6a^2b^2+4ab^3+b^4\right)+b\left(a^4+4a^3b+6a^2b^2+4ab^3+b^4\right)\)
\(x^5=\left(a+b\right)\left(a^4+4a^3b+6a^2b^2+4ab^3+b^4\right)\)
\(x^5=\left(a+b\right)\left[\left(a^4+3a^3b+3a^2b^2+ab^3\right)+\left(a^3b+3a^2b^2++3ab^3+b^4\right)\right]\)
\(x^5=\left(a+b\right)\left[a\left(a^3+3a^2b+3ab^2+b^3\right)+b\left(a^3+3a^2b+3ab^2+b^3\right)\right]\)
\(x^5=\left(a+b\right)^2\left(a^3+3a^2b+3ab^2+b^3\right)\)
\(x^5=\left(a+b\right)^2\left[\left(a^3+2a^2b+ab^2\right)+\left(a^2b+2ab^2+b^3\right)\right]\)
\(x^5=\left(a+b\right)^2\left[a\left(a^2+2ab+b^2\right)+b\left(a^2+2ab+b^2\right)\right]\)
\(x^5=\left(a+b\right)^3\left(a^2+2ab+b^2\right)\)
\(x^5=\left(a+b\right)^5\)
Bạn có thể tự tóm tắt lại
\(5a^3-10a^2b+5ab^2-10a+10b\)
\(=5a\left(a^2-2ab+b^2\right)-5\left(2a-2b\right)\)
\(=5a\left(a-b\right)^2-5\left(2a-2b\right)\)
\(=5\left[a\left(a-b\right)^2-\left(2a-2b\right)\right]\)
\(=5\left[a\left(a-b\right)^2-2\left(a-b\right)\right]\)
\(=5\left(a-b\right)\left[a\left(a-b\right)-2\right]\)
\(x^6-x^4+2x^3+2x^2\)
\(=x^4\left(x^2-1\right)+2x^2\left(x+1\right)\)
\(=x^4\left(x-1\right)\left(x+1\right)+2x^2\left(x+1\right)\)
\(=\left[x^4\left(x-1\right)+2x^2\right]\left(x+1\right)\)
\(=\left[x^5-x^4+2x^2\right]\left(x+1\right)\)
\(=x^2\left(x^3-x^2+2\right)\left(x+1\right)\)
5a3-10a2b+5ab2-10a+10b
=5a.(a2-2ab+b2) - 10.(a-b)
=5a.(a-b)2-10.(a-b)
=5(a-b).[a.(a-b) - 2]
x6-x4+2x3+2x2
= x4.(x2-1)+2x2.( x+1)
= x4.(x+1).(x-1) +2x2.(x+1)
= x2.(x+1).[x2.(x-1) + 2]
= x2.(x+1).(x3-x2+2)
a) \(x^4-4x^{3^{ }}+8x+3\)
\(=\left(x^4+x^3\right)-\left(5x^3+5x^2\right)+\left(5x^2+5x\right)+\left(3x+3\right)\)
\(=x^{3^{ }}\left(x+1\right)-5x^{2^{ }}\left(x+1\right)+5x\left(x+1\right)+3\left(x+1\right)\)
\(=\left(x+1\right)\left(x^3-5x^2+5x+3\right)\)
\(=\left(x+1\right)\left[\left(x^3-3x^2\right)-\left(2x^2-6x\right)-\left(x-3\right)\right]\)
\(=\left(x+1\right)\left[x^2\left(x-3\right)-2x\left(x-3\right)-\left(x-3\right)\right]\)
\(=\left(x+1\right)\left(x-3\right)\left(x^2-2x-1\right)\)
\(=\left(x+1\right)\left(x-3\right)\left[\left(x-1\right)^2-2\right]\)
\(=\left(x+1\right)\left(x-3\right)\left(x-1-\sqrt{2}\right)\left(x-1+\sqrt{2}\right)\)
b, \(x^2\left(y^2-4\right)^2-6x\left(y^2-4\right)+9\)
\(=\left[x\left(y^2-4\right)-3\right]^2\)
\(=\left(xy^2-4x-3\right)^2\)
\(x^8+x^7+1\)
\(=x^8+x^7+x^6-x^6+x^5-x^5+x^4-x^4+x^3-x^3+x^2-x^2+x-xx+1\)
\(=\left(x^8-x^6+x^5-x^3+x^2\right)\)
\(+\left(x^7-x^5+x^4-x^2+x\right)\)
\(+\left(x^6-x^4+x^3-x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^6-x^4+x^3-x+1\right)\)