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5 tháng 7 2016

a) \(x^2+4x+3=\left(x^2+4x+4\right)-1=\left(x+2\right)^2-1^2=\left(x+1\right)\left(x+3\right)\) (mình sửa lại)

b) \(x^2+8x-9=\left(x^2+8x+16\right)-25=\left(x+4\right)^2-5^2=\left(x-1\right)\left(x+9\right)\)

c) \(3x^2+6x-9=3\left[\left(x^2+2x+1\right)-4\right]=3\left[\left(x+1\right)^2-2^2\right]=3\left(x-1\right)\left(x+3\right)\)

d) \(2x^2+x-3=2x^2-4x+2+5x-5=2\left(x^2-2x+1\right)+5\left(x-1\right)=2\left(x-1\right)^2+5\left(x-1\right)=\left(x-1\right)\left(2x+3\right)\)

 

6 tháng 7 2016

tik nhé Toán lớp 8

Câu 2 nha

\(a,x^4+2x^3+x^2\)

\(=x^2\left(x^2+2x+1\right)\)

\(=x^2\left(x+1\right)^2\)

\(c,x^2-x+3x^2y+3xy^2+y^3-y\)

\(=\left(x^3+3x^2y+3xy^2+y^3\right)-\left(x+y\right)\)

\(=\left(x+y\right)^3-\left(x+y\right)\)

\(=\left(x+y\right)\left(x^2+2xy+y^2-1\right)\)

11 tháng 12 2018

a, x^2-4x+3

=x^2-x-3x+3

=x(x-1)-3(x-1)

=(x-3)(x-1)

11 tháng 12 2018

\(\left(x^2+x\right)^2+4x^2+4x-12\)

\(=x^4+2x^3+5x^2+4x-12\)

\(=x^4-x^3+3x^3-3x^2+8x^2-8x+12x-12\)

\(=x^3.\left(x-1\right)+3x^2.\left(x-1\right)+8x.\left(x-1\right)+12.\left(x-1\right)\)

\(=\left(x-1\right).\left(x^3+3x^2+8x+12\right)=\left(x-1\right).\left(x+2\right).\left(x^2+x+6\right)\)

p/s: sai sót bỏ qua

4 tháng 8 2017

a )\(x^2-2x-4y^2-4y=\left(x^2-2x+1\right)-\left(4y^2+4y+1\right)\)

\(=\left(x-1\right)^2-\left(2y+1\right)^2=\left(x-2y-2\right)\left(x+2y\right)\)

b )\(x^4+2x^3-4x-4=\left(x^4+2x^3+x^2\right)-\left(x^2+4x+4\right)\)

\(=\left(x^2+x\right)^2-\left(x+2\right)^2=\left(x^2+2x+2\right)\left(x^2-2\right)\)

c ) \(x^2\left(1-x^2\right)-4-4x^2=x^2-x^4-4-4x^2\)

\(=x^2-\left(x^2+2\right)^2=\left(x-x^2-2\right)\left(x^2+x+2\right)\)

4 tháng 8 2017

a.x2-2x-4y2-4y=(x2-4y2)-(2x+4y)=(x-2y)(x+2y)-2(x+2y)=(x+2y)(x-2y-2)

b.x4+2x3-4x-4=(x4-4)+(2x3-4x)=(x2-2)(x2+2)+2x(x2-2)=(x2-2)(x2+2x+2)

c.x2(1-x2)-4-4x2= -x4-3x2-4=x2-(x4+4x2+4)=x2-(x2+2)2=(x-x2-2)(x+x2+2)

3 tháng 9 2018

\(x^2-2x-4y^2-4y\)

\(=\left(x^2-4y^2\right)-\left(2x+4y\right)\)

\(=\left(x-2y\right)\left(x+2y\right)-2\left(x+2y\right)\)

\(=\left(x+2y\right)\left(x-2y-2\right)\)

1 tháng 10 2020

\begin{array}{l} a){\left( {ab - 1} \right)^2} + {\left( {a + b} \right)^2}\\  = {a^2}{b^2} - 2ab + 1 + {a^2} + 2ab + {b^2}\\  = {a^2}{b^2} + 1 + {a^2} + {b^2}\\  = {a^2}\left( {{b^2} + 1} \right) + \left( {{b^2} + 1} \right)\\  = \left( {{a^2} + 1} \right)\left( {{b^2} + 1} \right)\\ c){x^3} - 4{x^2} + 12x - 27\\  = {x^3} - 27 + \left( { - 4{x^2} + 12x} \right)\\  = \left( {x - 3} \right)\left( {{x^2} + 3x + 9} \right) - 4x\left( {x - 3} \right)\\  = \left( {x - 3} \right)\left( {{x^2} + 3x + 9 - 4x} \right)\\  = \left( {x - 3} \right)\left( {{x^2} - x + 9} \right)\\ b){x^3} + 2{x^2} + 2x + 1\\  = {x^3} + 2{x^2} + x + x + 1\\  = x\left( {{x^2} + 2x + 1} \right) + \left( {x + 1} \right)\\  = x{\left( {x + 1} \right)^2} + \left( {x + 1} \right)\\  = \left( {x + 1} \right)\left( {x\left( {x + 1} \right) + 1} \right)\\  = \left( {x + 1} \right)\left( {{x^2} + x + 1} \right)\\ d){x^4} - 2{x^3} + 2x - 1\\  = {x^4} - 2{x^3} + {x^2} - {x^2} + 2x - 1\\  = {x^2}\left( {{x^2} - 2x + 1} \right) - \left( {{x^2} - 2x + 1} \right)\\  = \left( {{x^2} - 2x + 1} \right)\left( {{x^2} - 1} \right)\\  = {\left( {x - 1} \right)^2}\left( {x - 1} \right)\left( {x + 1} \right)\\  = {\left( {x - 1} \right)^3}\left( {x + 1} \right)\\ e){x^4} + 2{x^3} + 2{x^2} + 2x + 1\\  = {x^4} + 2{x^3} + {x^2} + {x^2} + 2x + 1\\  = {x^2}\left( {{x^2} + 2x + 1} \right) + \left( {{x^2} + 2x + 1} \right)\\  = \left( {{x^2} + 2x + 1} \right)\left( {{x^2} + 1} \right)\\  = {\left( {x + 1} \right)^2}\left( {{x^2} + 1} \right) \end{array}

11 tháng 12 2019

a ) x3 - 2x2 + x

= x3 - x2 - x+ x

= ( x3 - x2 ) - ( x2 - x )

= x2 . ( x - 1 ) - x . ( x - 1 )

= ( x - 1 )( x2 - x )

b ) x3 - 3x2 - 4x + 12

= ( x3 - 3x2 ) - ( 4x - 12 )

=  x2 . ( x - 3 ) - 4 . ( x - 3 )

= ( x - 3 )( x2 - 4 )

= ( x - 3 )( x - 2 )( x + 2 )

20 tháng 4 2017

a) x2 – 4 + (x – 2)2

= (x2 – 22) + (x – 2)2 = (x – 2)(x + 2) + (x – 2)2

= (x – 2) [(x + 2) + (x – 2)]

= (x – 2)(x + 2 + x – 2)

= 2x(x – 2)

b) x3 – 2x2 + x – xy2

= x(x2 – 2x + 1 – y2) = x[(x2 – 2x + 1) – y2]

= x[(x – 1)2 – y2]

= x[(x – 1) + y] [(x – 1) – y]

= x(x – 1 + y)(x – 1 – y)

c) x3 – 4x2 – 12x + 27

= (x3 + 27) – 4x(x + 3)

= (x + 3)(x2 – 3x + 9) – 4x(x + 3)

= (x + 3)(x2 – 3x + 9 – 4x)

= (x + 3)(x2 – 7x + 9)

2 tháng 11 2016

a) (x2-4x+3)(x2-10x+24)+8=((x2-x)-(3x-3))((x2-6x)-(4x-24))+8

=(x(x-1)-3(x-1))(x(x-6)-4(x-6))+8=(x-1)(x-3)(x-4)(x-6)+8=((x-1)(x-6))(x-3)(x-4))+8

=(x2-7x+6)(x2-7x+12)+8

Đặt x2-7x+6=a

Ta có : a(a+6)+8=a2+6a+8=(a+2)(a+4)=(x2-7x+8)(x2-7x+10)=(x2-7x+8)(x-5)(x-2)

b) Tương tự như câu a kết quả là (x-3)(x3+9x2+21x+9)

c) x4+x3+6x2+3x+9=(x4+x3+3x2)+(3x2+3x+9)=x2(x2+x+3)+3(x2+x+3)=(x2+x+3)(x2+2)