Phân tích đa thức thành nhân tử:
\(\left(a-x\right)y^3-\left(a-y\right)x^3+\left(x-y\right)a^3\)
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Đặt \(x+y-z=a;x-y+z=b;y+z-x=c\)
Ta có:\(A=\left(a+b+c\right)^3-a^3-b^3-c^3\)
\(A=\left[\left(a+b\right)+c\right]^3-a^3-b^3-c^3\)
\(A=\left(a+b\right)^3+3\left(a+b\right)\cdot c\cdot\left(a+b+c\right)+c^3-a^3-b^3-c^3\)
\(A=a^3+b^3+3ab\left(a+b\right)+3\left(a+b\right)c\left(a+b+c\right)+c^3-a^3-b^3-c^3\)
\(A=3\left(a+b\right)\left(ab+ac+bc+c^2\right)\)
\(A=3\left(a+b\right)\left(b+c\right)\left(c+a\right)\)
Hay \(A=3\cdot2x\cdot2y\cdot2z\)
\(A=24xyz\)
a, \(x^3-2x-y^3+2y\) (sửa đề)
\(=\left(x^3-y^3\right)-\left(2x-2y\right)\)
\(=\left(x-y\right)\left(x^2+xy+y^2\right)-2\left(x-y\right)\)
\(=\left(x-y\right)\left(x^2+xy+y^2-2\right)\)
b, \(\left(x-y\right)\left(x+y\right)-4zx+4yz\)
\(=\left(x-y\right)\left(x+y\right)-\left(4zx-4yz\right)\)
\(=\left(x-y\right)\left(x+y\right)-4z\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y-4z\right)\)
Bạn xem lại đề câu a giúp mình nha!
a: \(\left(a+b+c\right)^3-a^3-b^3-c^3\)
\(=\left[\left(a+b+c\right)^3-a^3\right]-\left(b^3+c^3\right)\)
\(=\left(a+b+c-a\right)\left[\left(a+b+c\right)^2+a\left(a+b+c\right)+a^2\right]-\left(b+c\right)\left(b^2-bc+c^2\right)\)
\(=\left(b+c\right)\left[a^2+b^2+c^2+a^2+a^2+2ab+2bc+2ac+ab+ac-b^2+bc-c^2\right]\)
\(=\left(b+c\right)\left(3a^2+3ab+3bc+3ac\right)\)
\(=3\left(b+c\right)\left(a+b\right)\left(a+c\right)\)
b: \(=\left(2x+2y+2z\right)^3-\left(x+y\right)^3-\left[\left(y+z\right)^3+\left(x+z\right)^3\right]\)
\(=\left(x+y+2z\right)\left[\left(2x+2y+2z\right)^2+2\left(x+y+z\right)\left(x+y\right)+\left(x+y\right)^2\right]-\left(x+y+2z\right)\left[\left(y+z\right)^2-\left(y+z\right)\left(x+z\right)+\left(x+z\right)^2\right]\)
\(=3\left(x+y+2z\right)\left(x+z+2y\right)\left(y+z+2x\right)\)
a: \(a\left(x-y\right)-b\left(y-x\right)+c\left(x-y\right)\)
\(=a\left(x-y\right)+b\left(x-y\right)+c\left(x-y\right)\)
\(=\left(x-y\right)\left(a+b+c\right)\)
b: \(a^m-a^{m+2}\)
\(=a^m-a^m\cdot a^2\)
\(=a^m\left(1-a^2\right)\)
\(=a^m\left(1-a\right)\left(1+a\right)\)
Biến đổi : \(\left(x^2+y^2\right)^3+\left(z^2-x^2\right)^3\) theo công thức tổng của hai lập pương , ta được :
\(\left(y^2+z^2\right)\left[\left(x^2+y^2\right)^2-\left(x^2+y^2\right)\left(z^2-x^2\right)+\left(z^2-x^2\right)^2\right]\)
Thay vào \(A\),ta có : \(A=\left(y^2+z^2\right).B\).Trong đó :
\(B=\left[\left(x^2+y^2\right)^2-\left(x^2+y^2\right)\left(z^2-x^2\right)\right]+\left[\left(z^2-x^2\right)^2-\left(y^2+z^2\right)^2\right]\)
\(=\left[\left(x^2+y^2\right)\left(2x^2+y^2-z^2\right)\right]+\left[\left(2z^2-x^2+y^2\right)\left(-x^2-y^2\right)\right]\)
\(=\left(x^2+y^2\right)\left(3x^2-3z^2\right)\)
Vậy \(A=3\left(y^2+z^2\right)\left(x^2+y^2\right)\left(x^2-z^2\right)\).