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a/ 3(a + b) + c(a + b) = (a + b)(3 + c)
b/ (a - b)2 - c2 = (a - b - c)(a - b + c)
a) a2 + b2 + 2ab + 2a + 2b + 1
= (a2 + b2 + 2ab) + (2a + 2b) + 1
= (a + b)2 + 2(a + b) + 1
= (a + b + 1)2
b) a3 - 3a + 3b - b3
= (a3 - b3) - (3a - 3b)
= (a - b)(a2 - ab + b2) - 3(a - b)
= (a - b)(a2 - ab + b2 - 3)
c) x2 + 2x - 15
= (x2 + 2x + 1) - 16
= (x + 1)2 - 16
= (x + 1 - 5)(x + 1 + 5)
= (x - 4)(x + 6)
d) a4 + 6a2b + 9b2 - 1
= (a2 + 3b)2 - 1
= (a2 + 3b - 1)(a2 + 3b + 1)
BtA là hằng đẳng thức mà.còn B thi ????????????????????????????????
a) 3a2-6ab+3b2-12c2
=3.(a2-2ab+b2-4c2)
=3.[(a-b)2-4c2]
=3.(a-b-2c)(a-b+2c)
\(a^3-3a+3b-b^3=\left(a^3-b^3\right)-3\left(a-b\right)=\left(a-b\right)\left(a^2+b^2+ab-3\right)\)
\(x^2-2014x+2013=x^2-2013x-x+2013=x\left(x-2013\right)-\left(x-2013\right)=\left(x-2013\right)\left(x-1\right)\)
a3 - 3a + 3b - b3
= ( a3 - b3 ) - ( 3a - 3b )
= ( a - b )( a2 + ab + b2 ) - 3( a - b )
= ( a - b )( a2 + ab + b2 - 3 )
x2 - 2014x + 2013
= x2 - 2013x - x + 2013
= x( x - 2013 ) - ( x - 2013 )
= ( x - 2013 )( x - 1 )
Bài làm:
a) \(x^2-2xy+y^2-zx+yz\)
\(=\left(x-y\right)^2-z\left(x-y\right)\)
\(\left(x-y\right)\left(x-y-z\right)\)
a/ \(x^2-2xy+y^2-zx+yz.\)
\(=\left(x-y\right)^2-z\left(x-y\right)\)
\(=\left(x-y\right)\left(x-y-z\right)\)
c/ \(x^2-y^2-2x-2y.\)
\(=x^2-2x+1-y^2-2y-1\)
\(=\left(x^2-2x+1\right)-\left(y^2+2y+1\right)\)
\(=\left(x-1\right)^2-\left(y+1\right)^2\)
\(=\left(x-1+y+1\right)\left(x-1-y-1\right)\)
\(=\left(x+y\right)\left(x-y-2\right)\)
3a-3b+a^2-2ab+b^2
=(3a-3b)+(a2-2ab+b2)
=3(a-b)+(a-b)2
=(a-b)[3+(a-b)]
=(a-b)(3+a-b)