Phân tích đa thức:
(x-y)-3x(y-x)
Làm ơn giúp e với ạ , xíu nữa thầy bắt nộp rùi huhu:((
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a) \(3\left(x-y\right)^2+9y\left(y-x\right)^2\)
\(=3\left(x-y\right)^2+9y\left(x-y\right)^2\)
\(=\left(x-y\right)^2\left(3-9y\right)\)
\(=3\left(x-y\right)^2\left(3y+1\right)\)
b) \(3\left(x-y\right)^2+9y\left(y-x\right)\)
\(=3\left(y-x\right)^2+9y\left(y-x\right)\)
\(=\left(y-x\right)\left[3\left(y-x\right)+9y\right]\)
\(=3\left(y-x\right)\left(y-x+3y\right)\)
\(=3\left(y-x\right)\left(4y-x\right)\)
a: =3(x-y)^2+9y(x-y)^2
=(x-y)^2(3+9y)
=(x-y)^2*3*(y+3)
b: =3(x-y)^2-9y(x-y)
=3(x-y)(x-y-9y)
=3(x-y)(x-10y)
\(5x\left(x-1\right)-x\left(x-1\right)\)
\(=\left(x-1\right)\left(5x-x\right)\)
\(=4x\left(x-1\right)\)
b) \(x^2\left(x+1\right)-x\left(x+1\right)\)
\(=\left(x+1\right)\left(x^2-x\right)\)
\(=x\left(x+1\right)\left(x-1\right)\)
c) \(x^2+4y^2+4xy\)
\(=\left(x+2y\right)^2\)
\(\left(x+y+z\right)^5-x^5-y^5-z^5\)
Xét phương trình: \(\left(x+y+z\right)^5-x^5-y^5-z^5=0\)
Có nghiệm: \(x=-y;x=-z;y=-z\)
Hệ số của mũ là: 5
\(\Rightarrow\left(x+y+z\right)^5-x^5-y^5-z^5\)
\(=5\left(x+y\right)\left(y+z\right)\left(z+x\right)\left(x^2+y^2+z^2+xy+yz+xz\right)\)
Hok Tốt!!!
a) \(9\left(x+y-1\right)^2-4\left(2x+3y+1\right)^2\)
\(=\left(3x+3y-3\right)^2-\left(4x+6y+2\right)^2\)
\(=\left(3x+3y-3-4x-6y-2\right)\left(3x+3y-3+4x+6y+2\right)\)
\(=\left(-x-3y-5\right)\left(7x+9y-1\right)\)
b) \(3x^4y^2+3x^3y^2+3xy^2+3y^2\)
\(=\left(3x^4y^2+3xy^2\right)+\left(3x^3y^2+3y^2\right)\)
\(=3xy^2\left(x^3+1\right)+3y^2\left(x^3+1\right)\)
\(=\left(3xy^2+3y^2\right)\left(x^3+1\right)\)
\(=3y^2\left(x+1\right)\left(x+1\right)\left(x^2-x+1\right)\)
\(=3y^2\left(x+1\right)^2\left(x^2-x+1\right)\)
c) \(\left(x+y\right)^3-1-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left[\left(x+y\right)^2+x+y+1\right]-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left(x^2+2xy+y^2+x+y+1-3xy\right)\)
\(=\left(x+y-1\right)\left(x^2+x+y^2+y+1-xy\right)\)
Bài 1: Ta có: \(A=1+4y-y^2=5-\left(y^2-4y+4\right)=5-\left(y-2\right)^2\le5\)
Dấu "=" xảy ra khi \(\left(y-2\right)^2=0\Rightarrow y-2=0\Rightarrow y=2\)
Vậy \(maxA=5\) khi \(y=2\)
Bài 2: Ta có: \(a^3+b^3+3ab=\left(a^3+3a^2b+3ab^2+b^3\right)-3a^2b-3ab^2+3ab\)
\(=\left(a+b\right)^3-3ab\left(a+b-1\right)=1-0=1\)
\(P=\sqrt[]{x}+\dfrac{3}{\sqrt[]{x}-1}\left(x>1\right)\)
\(P=\sqrt[]{x}-1+\dfrac{3}{\sqrt[]{x}-1}+1\)
Áp dụng bất đẳng thức Cauchy cho 2 số \(\sqrt[]{x}-1;\dfrac{3}{\sqrt[]{x}-1}\) ta được :
\(\sqrt[]{x}-1+\dfrac{3}{\sqrt[]{x}-1}\ge2\sqrt[]{\sqrt[]{x}-1.\dfrac{3}{\sqrt[]{x}-1}}\)
\(\Rightarrow\sqrt[]{x}-1+\dfrac{3}{\sqrt[]{x}-1}\ge2\sqrt[]{3}\)
\(\Rightarrow P=\sqrt[]{x}-1+\dfrac{3}{\sqrt[]{x}-1}+1\ge2\sqrt[]{3}+1\)
\(\Rightarrow Min\left(P\right)=2\sqrt[]{3}+1\)
này lam123 nói thế vẫn chưa hiểu à ko đăng linh tinh
(x-y)-3x(y-x)
=(x-y)+3x(x-y)
=(x-y)(1+3x)
#H