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21 tháng 8 2017

a)\(\left(3x-1\right)^2-16=\left(3x-1-16\right)\left(3x-1+16\right)\)

                                     \(=\left(3x-17\right)\left(3x+15\right)\)

c)\(\left(2x+5\right)^2-\left(x-9\right)^2=\left(2x+5+x-9\right)\left(2x+5-x+9\right)\)

                                                 \(=\left(x-4\right)\left(x+14\right)\)

      Aps dungj t/c a2 - b2 = ( a-b)(a+b)

14 tháng 10 2017

a. 6x3y2 ( 2-x) + 9x2y2 (x-2)

= -6x3y2 (x-2) + 9x2y( x-2)

= (x-2) 3x2y2 ( -2x + 3)

b. x2 - 4x + 4y - y

= x- y2 - (4x - 4y )

= (x-y)(x+y) - 4( x-y)

= (x-y)(x+y-4)

c. 81x+ 6yz -9y2-z2 

= 81x - (9y2 - 6yz + z2 )

= (9x)2 - ( 3y - z )2

= (9x + 3y -z)(9x - 3y + z )

14 tháng 10 2017

\(a,=6x^3y^2\left(2-x\right)-9x^2y^2\left(2-x\right)\)

\(=\left(2-x\right)\left(6x^3y^2-9x^2y^2\right)=\left(2-x\right)3x^2y^2\left(2x-3\right)\)

\(f,=\left(x-3-x-2\right)\left(x-3+x+2\right)\)

\(=-5\left(2x-1\right)\)

\(g,=\left(x-3\right)\left(x+3\right)+2\left(x+3\right)\)

\(=\left(x+3\right)\left(x-3+2\right)\)

\(=\left(x+3\right)\left(x-1\right)\)

a) Ta có: \(\left(4x^2-3x-18\right)^2-\left(4x^2+3x\right)^2\)

\(=\left(4x^2-3x-18-4x^2-3x\right)\left(4x^2-3x-18+4x^2+3x\right)\)

\(=\left(-6x-18\right)\left(8x^2-18\right)\)

\(=-6\left(x+3\right)\cdot2\left(4x^2-9\right)\)

\(=-12\left(x+3\right)\left(2x-3\right)\left(2x+3\right)\)

b) Ta có: \(9\left(x+y-1\right)^2-4\left(2x+3y+1\right)^2\)

\(=\left(3x+3y-3\right)^2-\left(4x+6y+2\right)^2\)

\(=\left(3x+3y-3-4x-6y-2\right)\left(3x+3y-3+4x+6y+2\right)\)

\(=-\left(x+3y+5\right)\left(7x+9y-1\right)\)

c) Ta có: \(-4x^2+12xy-9y^2+25\)

\(=-\left(4x^2-12xy+9y^2-25\right)\)

\(=-\left[\left(2x-3y\right)^2-25\right]\)

\(=-\left(2x-3y-5\right)\left(2x-3y+5\right)\)

d) Ta có: \(x^2-2xy+y^2-4m^2+4mn-n^2\)

\(=\left(x^2-2xy+y^2\right)-\left(4m^2-4mn+n^2\right)\)

\(=\left(x-y\right)^2-\left(2m-n\right)^2\)

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

10 tháng 9 2016

a) \(x^2-81=\left(x-9\right)\left(x+9\right)\)

b) \(4x^2-25=\left(2x-5\right)\left(2x+5\right)\)

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

d) \(x^2+6xy+9y^2=\left(x+3y\right)^2\)

e) \(6x-9-x^2=-\left(x^2-6x+9\right)=-\left(x-3\right)^2\)

f) \(x^2-4x^2+4y^2+4xy=\left(x^2+4xy+4y^2\right)-4x^2=\left(x+2y\right)^2-4x^2\\ =\left(x+2y+2x\right)\left(x+2y-2x\right)=\left(3x+2y\right)\left(2y-x\right)\)

g) \(\left(a+b\right)^3+\left(a-b\right)^3=\left(a+b+a-b\right)\left[\left(a+b\right)^2-\left(a+b\right)\left(a-b\right)+\left(a-b\right)^2\right]\)

\(=2a\left(a^2+2ab+b^2-a^2+b^2+a^2-2ab+b^2\right)=2a\left(a^2+3b^2\right)\)

h) \(\left(3x+1\right)^2-\left(x+1\right)^2=\left(3x+1+x+1\right)\left(3x+1-x-1\right)\\ =\left(4x+2\right)\cdot2x=4x\left(2x+1\right)\)

4 tháng 11 2018

a) \(2x^2-2y^2\)

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

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

b) \(x^2-4x+4\)

\(=x^2-2\cdot x\cdot2+2^2\)

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

c) \(x^2+2x+1-y^2\)

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

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

d) \(x^2-4x\)

\(=x\left(x-4\right)\)

e) \(x^2+10x+25\)

\(=x^2+2\cdot x\cdot5+5^2\)

\(=\left(x+5\right)^2\)

g) \(x^2-2xy+y^2-9\)

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

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

h) \(2x^2-2\)

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

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

i) \(5x^2-5xy+9x-9y\)

\(=5x\left(x-y\right)+9\left(x-y\right)\)

\(=\left(x-y\right)\left(5x+9\right)\)

k) \(y^2-4y+4-x^2\)

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

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

l) \(x^2-16\)

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

\(=\left(x-4\right)\left(x+4\right)\)

m) \(3x^2-3xy+2x-2y\)

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

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

o) \(3x^4-6x^3+3x^2\)

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

\(=3x^2\left(x-1\right)^2\)

4 tháng 11 2018

a) 2x2 - 2y2

 = (2x - 2y)(2x + 2y)

 = 4(x - y)(x + y)

b) x2 - 4x + 4

 = (x - 2)2

c) x+ 2x + 1 - y2

 = (x + 1)2 - y2

 = (x + 1 - y)(x + 1 + y)

d) x2 - 4x 

 = x(x - 4)

e) x+10x + 25

 = (x + 5)2

g) x2 - 2xy + y2 - 9

= (x - y)2 - 32

 = (x - y - 3)(x - y + 3)

h) 2x2 - 2

= 2(x2 - 1) 

 = 2(x - 1)(x + 1)

i) 5x- 5xy + 9x - 9y

  = 5x(x - y) + 9(x- y)

 = (5x + 9)(x - y)

k) y2 - 4y + 4 - x2

 = (y - 2)2 - x2

 = (y - 2 - x)(y - 2 + x)

l) x- 16

 = x- 42

 = (x - 4)(x + 4)

m) 3x2 - 3xy + 2x -2y

 = 3x(x - y) +2(x-y)

 = (3x + 2)(x - y)

o) 3x- 6x+ 3x2

 = 3x4 - 3x3 - 3x3 + 3x2

 = 3x3(x - 1) - 3x2(x - 1)

 = (3x- 3x2)(x - 1)

 = 3x2(x - 1)(x - 1)

 = 3x2.(x - 1)2