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a) 9x^2+6xy+y^2
=(3x+y)2
b)6x - 9 - x^2
=-(x2-6x+9)
=-(x-3)2
c) x^2 + 4y^2 + 4xy
=(x+2y)2
9x2 + 6xy + y2
= (3x)2 + 2.3x.y + y2
= (3x + y)2
b) 6x - 9 - x2
= -(x2 - 6x + 9)
= -(x - 3)2
phân tích thành nhân tử:
\(x^2-9=x^2-3^2=\left(x+3\right)\left(x-3\right)\)
\(4x^2-25=\left(2x\right)^2-5^2=\left(2x+5\right)\left(2x-5\right)\)
\(x^6-y^6=\left(x^3\right)^2-\left(y^3\right)^2\)\(=\left(x^3+y^3\right)\left(x^3-y^3\right)\)
\(=\left(x+y\right)\left(x-y\right)\left(x^2+xy+y^2\right)\left(x^2-xy+y^2\right)\)
\(9x^2+6xy+y^2=\left(3x\right)^2+2\cdot3x\cdot1+y^2=\left(3x+y\right)^2\)
\(x^2+4y^2+4xy=x^2+2\cdot x\cdot2y+\left(2y\right)^2=\left(x+2y\right)^2\)
a. \(x^3-0.25x=0\Rightarrow x\left(x^2-\frac{1}{4}\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x^2-\frac{1}{4}=0\end{cases}\Rightarrow\orbr{\begin{cases}x=0\\x^2=\frac{1}{4}\end{cases}}}\) \(\Rightarrow\orbr{\begin{cases}x=0\\\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{-1}{2}\end{cases}}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=0\\\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{-1}{2}\end{cases}}\end{cases}}\)=> \(x\in\left\{0;\frac{1}{2};\frac{-1}{2}\right\}\)
b, \(x^2-10x=-25\)\(\Rightarrow x^2-10x+25=0\)
\(\Rightarrow\left(x-5\right)^2=0\Rightarrow x-5=0\Rightarrow x=5\)
a, \(x^2-9=x^2-3x+3x-9\)
\(=x\left(x-3\right)+3\left(x-3\right)=\left(x-3\right)\left(x+3\right)\)
b, \(4x^2-25=\left(2x\right)^2-5^2=\left(2x-5\right)\left(2x+5\right)\)
c, \(x^6-y^6=\left(x^3\right)^2-\left(y^3\right)^2=\left(x^3+y^3\right)\left(x^3-y^3\right)\)
d, \(9x^2+6xy+y^2=\left(3x\right)^2+2\left(3xy\right)+y^2\) \(=\left(3x+y\right)^2\)
e, \(6x-9-x^2=6x-18+9-x^2\) \(=6\left(x-3\right)-\left(x-3\right)\left(x+3\right)\)
\(=\left(x-3\right)\left(6-x-3\right)=\left(x-3\right)\left(3-x\right)\)
f, \(x^2+4y^2+4xy=x^2+2\left(2xy\right)+\left(2y\right)^2\)
\(\left(x+2y\right)^2\)
\(\)
a)x3-6x2+9x=x(x2-6x+9)=x(x-3)2
b)x2-2x-4y2-4y=(x2-2x+1)-(4y2+4y+1)=(x-1)2-(2y+1)2=(x-1-2y-1)(x-1+2y+1)=(x-2y-2)(x+2y)
c)x2-x+xy-y=x(x-1)+y(x-1)=(x-1)(x+y)
d)3x2-6xy-75+3y2=3[(x2-2xy+y2)-25]=3[(x-y)2-52]=3(x-y-5)(x-y+5)
e)2x2-5x-7=(2x2+2x)-(7x+7)=2x(x+1)-7(x+1)=(x+1)(2x-7)
f)x4+36=x4+12x2+36-12x2=(x2+6)2-12x2=(x2-\(\sqrt{12}x\)+6)(x2+\(\sqrt{12}x\)+6)
h)x4+4y4=x4+4x2y2+4y2-4x2y2=(x2+2y2)-4x2y2=(x2+2y2-2xy)(x2+2y2+2xy)
a)\(6x-9-x^2\)
\(=-\left(x^2+6x+9\right)\)
\(=-\left(x+3\right)^2\)
b)\(x^2+4y^2+4xy\)
\(=\left(x+2y\right)^2\)
c)\(x^2+8x+16\)
\(=\left(x+4\right)^2\)
d)\(9x^2-12xy+4y^2\)
\(=\left(3x-2y\right)^2\)
e)\(-25x^2y^2+10xy-1\)
\(=-\left(25x^2y^2-10xy+1\right)\)
\(=-\left(5xy-1\right)^2\)
f)\(4x^2-4x+1\)
\(=\left(2x-1\right)^2\)
j)\(x^2+6x+9\)
\(=\left(x+3\right)^2\)
h)\(9x^2-6x+1\)
\(=\left(3x-1\right)^2\)
#H
a, 6x - 9 - x2 = - x2 + 6x - 9 = - (x2 - 6x + 9) = - (x - 3)2
b, x2 + 4y2 + 4xy = x2 + 2. x . 2y + (2y)2 = (x + 2y)2
c, x2 + 8x + 16 = x2 + 2 . x . 4 + 42 = (x + 4)2
d, 9x2 - 12xy + 4y2 = (3x)2 - 2 . 3x . 2y + (2y)2 = (3x - 2y)2
e, - 25x2y2 + 10xy - 1 = - (25x2y2 - 10xy + 1) = - [(5xy)2 - 2 . 5xy + 1] = - (5xy - 1)2
f, 4x2 - 4x + 1 = (2x)2 - 2 . 2x + 1 = (2x - 1)2
j, x2 + 6x + 9 = x2 + 2 . x . 3 + 32 = (x + 3)2
h, 9x2 - 6x + 1 = (3x)2 - 2 . 3x + 1 = (3x - 1)2
a: 2x^2y-50xy=2xy(x-25)
b: 5x^2-10x=5x(x-2)
c: 5x^3-5x=5x(x^2-1)=5x(x-1)(x+1)
d: \(x^2-xy+x=x\left(x-y+1\right)\)
e: x(x-y)-2(y-x)
=x(x-y)+2(x-y)
=(x-y)(x+2)
f: 4x^2-4xy-8y^2
=4(x^2-xy-2y^2)
=4(x^2-2xy+xy-2y^2)
=4[x(x-2y)+y(x-2y)]
=4(x-2y)(x+y)
f1: x^2ỹ-y^2+y
=(x-y)(x+y)+(x+y)
=(x+y)(x-y+1)
a, \(9x^2+6xy+y^2=\left(3x\right)^2+2\times3xy+y^2=\left(3x+y\right)^2\)
b, \(6x-9-x^2=-\left(x^2-2\times3x+3^2\right)=-\left(x-3\right)^2\)
c, \(x^2+4y^2+4xy=x^2+2\times2xy+\left(2y\right)^2=\left(x+2y\right)^2\)