phân tích đa thức sau thành nhân tử dựa vào pp nhóm hạng tử :
ab(x^2+y^2) - xy(a^2+b^2)
x^4+25x^2+20x-4
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a: \(x^4+25x^2+20x-4\)
\(=x^4-5x^3+2x^2+5x^3-25x^2+10x-2x^2+10x-4\)
\(=x^2\left(x^2-5x+2\right)+5x\left(x^2-5x+2\right)-2\left(x^2-5x+2\right)\)
\(=\left(x^2-5x+2\right)\left(x^2+5x-2\right)\)
b: \(=x^4-6x^2-x^2+9\)
\(=\left(x^2-3\right)^2-x^2\)
\(=\left(x^2-x-3\right)\left(x^2+x-3\right)\)
c: \(=abx^2+aby^2-a^2xy-b^2xy\)
\(=\left(abx^2-b^2xy\right)+\left(aby^2-a^2xy\right)\)
\(=xb\left(ax-by\right)+ay\left(by-ax\right)\)
\(=\left(ax-by\right)\cdot\left(xb-ay\right)\)
1/(x+2)2 -(3x-1)2=(x+2+3x-1)(x+2-3x+1)=4x(-2x+3)=-8x2+12x
2/(x4+x2)(-2x3-2x)=x2(x2+1)-2x(x2+1)=(x2+1)(x2-2x)
Bài làm
-x2 - y2 + xy + 16
= -( x2 - xy + y2 ) + 16
= -( x - y )2 + 42
= -[ ( x - y )2 - 42 ]
= - [ ( x - y - 4 )( x - y + 4 ) ]
# Học tốt #
a)
\(=x^2\left(2x+3\right)+\left(2x+3\right)\)
\(=\left(x^2+1\right)\left(2x+3\right)\)
b)
\(=a\left(a-b\right)+a-b\)
\(=\left(a+1\right)\left(a-b\right)\)
c)
\(=2\left(x^2+2x+1-y^2\right)\)
\(=2\left(x+1-y\right)\left(x+1+y\right)\)
d)
\(=x^3\left(x-2\right)+10x\left(x-2\right)\)
\(=x\left(x^2+10\right)\left(x-2\right)\)
e)
\(=x\left(x^2+2x+1\right)\)
\(=x\left(x+1\right)^2\)
f)
\(=y\left(x+y\right)-\left(x+y\right)\)
\(=\left(y-1\right)\left(x+y\right)\)
a,2x3+3x2+2x+3
=(2x3+2x)+(3x2+3)
=2x(x2+1)+3(x2+1)
=(x2+1)(2x+3)
b,a2-ab+a-b
=(a2-ab)+(a-b)
=a(a-b)+(a-b)
=(a-b)(a+1)
c,2x2+4x+2-2y2
=2(x2+2x+1-y2)
=2[(x2+2x+1)-y2 ]
=2[(x+1)2-y2 ]
=2(x+1-y)(x+1+y)
d,x4-2x3+10x2-20x
=(x4-2x3)+(10x2-20x)
=x3(x-2)+10x(x-2)
=(x-2)(x3+10x)
=(x-2)[x(x2+10)]
e,x3+2x2+x
=x(x2+2x+1)
=x(x+1)2
f,xy+y2-x-y
=(xy+y2)-(x-y)
=y(x+y)-(x+y)
=(x+y)(y-1)
a ) xy + 1 - x - y
= x ( y - 1 ) + 1 - y
= x ( y - 1 ) - ( y - 1 )
= ( x - 1 ) ( y - 1 )
b ) x2 + ab + ac + bx
= ( b + x )x + a( b + c )
= ( b + x )1x + 1a( b + c )
= ( b + x ) ( x + a ) ( b + c )
c ) ax + bx - cx + a + b - c
= ( a + b - c )x + a + b - c
= ( a + b - c )x + ( a + b - c )1
= ( a + b - c ) ( x + 1 )
\(1,\\ a,=4\left(x-2\right)^2+y\left(x-2\right)=\left(4x-8+y\right)\left(x-2\right)\\ b,=3a^2\left(x-y\right)+ab\left(x-y\right)=a\left(3a+b\right)\left(x-y\right)\\ 2,\\ a,=\left(x-y\right)\left[x\left(x-y\right)^2-y-y^2\right]\\ =\left(x-y\right)\left(x^3-2x^2y+xy^2-y-y^2\right)\\ b,=2ax^2\left(x+3\right)+6a\left(x+3\right)\\ =2a\left(x^2+3\right)\left(x+3\right)\\ 3,\\ a,=xy\left(x-y\right)-3\left(x-y\right)=\left(xy-3\right)\left(x-y\right)\\ b,Sửa:3ax^2+3bx^2+ax+bx+5a+5b\\ =3x^2\left(a+b\right)+x\left(a+b\right)+5\left(a+b\right)\\ =\left(3x^2+x+5\right)\left(a+b\right)\\ 4,\\ A=\left(b+3\right)\left(a-b\right)\\ A=\left(1997+3\right)\left(2003-1997\right)=2000\cdot6=12000\\ 5,\\ a,\Leftrightarrow\left(x-2017\right)\left(8x-2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=2017\\x=\dfrac{1}{4}\end{matrix}\right.\\ b,\Leftrightarrow\left(x-1\right)\left(x^2-16\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=4\\x=-4\end{matrix}\right.\)
\(ab\left(x^2+y^2\right)-xy\left(a^2+b^2\right)\)
\(=abx^2+aby^2-a^2xy-b^2xy\)
\(=\left(abx^2-b^2xy\right)-\left(a^2xy-aby^2\right)\)
\(=bx\left(ax-by\right)-ay\left(ax-by\right)\)
\(=\left(ax-by\right)\left(bx-ay\right)\)