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28 tháng 7 2017

a, \(\left(x^2-2x\right)\left(x^2-2x-1\right)-6\)

Đặt \(x^2-2x=a\)

Thay vào biểu thức ta đc:

\(a.\left(a-1\right)-6=a^2-a-6\) \(=a^2-3a+2a-6=a\left(a-3\right)+2\left(a-3\right)\)

\(=\left(a-3\right).\left(a+2\right)\)

\(\Rightarrow\left(x^2-2x\right)\left(x^2-2x-1\right)-6=\left(x^2-2x-3\right)\left(x^2-2x+2\right)\)

b, \(\left(x^2+x+4\right)^2+8x\left(x^2+x+4\right)+15x^2\)

\(=\left[\left(x^2+x+4\right)^2+6x\left(x^2+x+4\right)+9x^2\right]+\left[2x\left(x^2+x+4\right)+6x^2\right]\)

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

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

28 tháng 7 2017

bn ơi câu a bn biến đổi ra a2-a-6 vậy -1 đâu bn

29 tháng 7 2016

1/ \(\left(x^2+x+4\right)^2+8x\left(x^2+x+4\right)+15x^2=x^4+10x^3+32x^2+40x+16\)(làm tắt nhưng chắc bạn tự hiểu đc)

\(=\left(x^4+2x^3\right)+\left(4x^2+2x^3\right)+\left(12x^2+6x^3\right)+\left(4x^2+8x\right)+\left(12x^2+24x\right)+\left(8x+16\right)\)

\(=x^3\left(x+2\right)+2x^2\left(2+x\right)+6x^2\left(2+x\right)+4x\left(x+2\right)+12x\left(x+2\right)+8\left(x+2\right)\)

\(=\left(x+2\right)\left(x^3+2x^2+6x^2+4x+12x+8\right)=\left(x+2\right)\left(x^3+8x^2+16x+8\right)\)

\(=\left(x+2\right)\left[\left(x^3+2x^2\right)+\left(6x^2+12x\right)+\left(4x+8\right)\right]=\left(x+2\right)\left[x^2\left(x+2\right)+6x\left(x+2\right)+4\left(x+2\right)\right]\)

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

29 tháng 7 2016

2/ \(\left(x+2\right)\left(x+4\right)\left(x+6\right)\left(x+8\right)+16=x^4+20x^3+140x^2+400x+400\)

\(=\left(x^4+10x^3+20x^2\right)+\left(10x^3+100x^2+200x\right)+\left(20x^2+200x+400\right)\)

\(=x^2\left(x^2+10x+20\right)+10x\left(x^2+10x+20\right)+20\left(x^2+10x+20\right)\)

\(=\left(x^2+10x+20\right)\left(x^2+10x+20\right)=\left(x^2+10x+20\right)^2\)

\(x^3+x^2+9x-10x^2-10x+25x+25\)

\(=x^2\left(x+1\right)-10x\left(x+1\right)+25\left(x+1\right)\)

\(=\left(x+1\right)\left(x^2-10x+25\right)=\left(x+1\right)\left(x-5\right)^2\)

26 tháng 7 2019

tao dep trai lam

26 tháng 6 2016

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

b) \(x^3-5x^2+8x-4=x^3-x^2-4x^2+4x+4x-4=x^2\left(x-1\right)-4x\left(x-1\right)+4\left(x-1\right)\)

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

c) \(2x^3-12x^2+17x-2=2x^3-4x^2-8x^2+16x+x-2=2x^2\left(x-2\right)-8x\left(x-2\right)+\left(x-2\right).\)

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

d) \(2x^4+x^3-22x^2+15x+36=2x^4+2x^3-x^3-x^2-21x^2-21x+36x+36.\)

\(=2x^3\left(x+1\right)-x^2\left(x+1\right)-21x\left(x+1\right)+36\left(x+1\right)\)

\(=\left(x+1\right)\left(2x^3-x^2-21x+36\right)\)

21 tháng 10 2018

a)\(6x^2-9xy\)

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

b)\(x^2-y^2-3x+3y\)

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

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

21 tháng 10 2018

c)\(x^4-8x^2-9\)

\(=x^4+x^2-9x^2-9\)

\(=x^2\left(x^2+1\right)-9\left(x^2+1\right)\)

\(=\left(x^2-9\right)\left(x^2+1\right)\)

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

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

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

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

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

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

16 tháng 11 2017

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

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

2,\(=x^3-5x^2-4x^2+20x-5x+25=x^2\left(x-5\right)-4x\left(x-5\right)-5\left(x-5\right)\)

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

17 tháng 10 2015

A) 1/2 x(x^2-4)+4(x+2)

=1/2x(x-2)(x+2)+4(x+2)

=(x+2)(1/2x^2-x+4)

b) 21(x-y)^2-7(x-y)^3

= (x-y)^2(21-7x+7y)

=(x-y)^2.7(3-x+y)

c) 1/8x^3-3/4x^2+3/2x-1

=(1/2x)^3-3.(1/2x)^2.1+3.1/2x.1^2-1

=(1/2x-1)^3