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a.
\(\left(3x+1\right)^2-\left(x+1\right)^2\\ =2x\left(4x+2\right)\)
b.https://hoc24.vn/hoi-dap/question/531769.html
Mình làm bài này r ; mà nó dài nên k mún làm lại
c.
\(5x^2-10xy+5y^2-20z^2\\ =5\left(x^2-2xy+y^2-4z^2\right)\\ =5\left(\left(x-y\right)^2-4z^2\right)\\ =5\left(x-y-2z\right)\left(x-y+2z\right)\)
m)
\(x^4+4\\ =\left(x^4+4x^2+4\right)-4x^2\\ =\left(x^2+2\right)^2-4x^2\\ =\left(x^2+2-2x\right)\left(x^2+2+2x\right)\)
câu 20
\(\)\(C_{20}=\left(a^2+1\right)^2-4a^2=\left(a^2+1\right)^2-\left(2a\right)^2=\left[\left(a^2+1\right)-2a\right]\left[\left(a^2+1\right)+2a\right]\)\(C_{20}=\left[a^2-2a+1\right]\left[a^2+2a+1\right]=\left(a-1\right)\left(a-1\right)\left(a+1\right)\left(a+1\right)\)
\(C_{20}=\left(a-1\right)\left(a-1\right)\left(a+1\right)\left(a+1\right)\)
a)x2-y2-5x+5y
=(x-y)(x+y)-5.(x-y)
=(x-y)(x+y-5)
b)5x3-5xy-10x2+10xy
=5x3+5xy-10x2
=5x.(x2+y-2x)
c)x3-3x2+1-3x
=x3+1-3x2-3x
=(x+1)(x2-x+1)-3x.(x+1)
=(x+1)(x2-x+1-3x)
=(x+1)(x2-4x+1)
d)3x2-6xy+3y2-12z2
=3.(x2-2xy+y2-4z2)
=3.[(x-y)2-4z2]
=3.(x-y-2z)(x-y+2z)
1/a ) = (x+y)3 -(x+y)
= (x+y)[(x+y)2+1]
c) = 5(x2-xy+y2)-20z2
=5(x-y)2-20z2
= 5 [ (x-y)2- 4z2 ]
=5(x-y-4z)(x-y+4z)
Bài 1:
a) x3-x+3x2y+3xy2+y3-y
=x3+2x2y-x2+xy2-xy+x2y+2xy2-xy+y3-y2+x2+2xy-x+y2-y
=x(x2+2xy-x+y2-y)+y(x2+2xy-x+y2-y)+(x2+2xy-x+y2-y)
=(x2+2xy-x+y2-y)(x+y+1)
=[x(x+y-1)+y(x+y-1)](x+y+1)
=(x+y-1)(x+y)(x+y+1)
c) 5x2-10xy+5y2-20z2
=-5(2xy-y2+4z2-2)
Bài 2:
5x(x-1)=x-1
=>5x2-6x+1=0
=>5x2-x-5x+1
=>x(5x-1)-(5x-1)
=>(x-1)(5x-1)=0
=>x=1 hoặc x=1/5
b) 2(x+5)-x2-5x=0
=>2(x+5)-x(x+5)=0
=>(2-x)(x+5)=0
=>x=2 hoặc x=-5
Câu a trước đi ạ ^^
a) 7x - 6x2 - 2
= - 6x2 + 7x - 2
= (- 6x2 + 3x) + (4x - 2)
= 3x (- 2x + 1) + 2 (2x-1)
= - 3x ( 2x -1) + 2 (2x - 1)
= ( 2x -1 ) ( - 3x +2 )
d)
x3 + 2x2y+ xy2 - 9x
=x*(x2+2xy+y2 -9)
=x*[ (x+y)2 -32 ]
=x * (x+y-3) * (x+y-3)
a )
\(5x^2-10xy+5y^2-20z^2\)
\(=5\left(x^2-2xy+y^2-4z^2\right)\)
\(=5\left[\left(x-y\right)^2-4z^2\right]\)
b )
\(-5x^2-16x-3\)
\(=-5x^2-15x-x-3\)
\(=-5x\left(x+3\right)-\left(x+3\right)\)
\(=\left(-5x-1\right)\left(x+3\right)\)
c )
\(x^2-5x+5y-y^2\)
\(=\left(x^2-y^2\right)-5\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)\)
\(=\left(x-y\right)\left[\left(x+y\right)-5\right]\)
d )
\(3x^2-6xy+3y^2-12z^2\)
\(=3\left(x^2-2xy+y^2-4z^2\right)\)
\(=3\left[\left(x-y\right)^2-4z^2\right]\)
P/s : Mình bổ sung :
a )
\(=5\left(x-y-2z\right)\left(x-y+2z\right)\)
d )
\(=3\left(x-y-2z\right)\left(x-y+2z\right)\)