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a) x2 +x -y2 + y = ( x2 -y2 ) +(x+y)
= (x-y)(x+y) +(x+y)
=(x+y)( x-y+1)
b) 3x2 +3y2 -6xy -12 = 3(x2 +y2 - 2xy) -12
=3 [ (x-y)2 -4]
= 3( x-y-2)(x-y+2)
a) x2 + x - y2 + y
= (x2 - y2) + (x + y)
= (x + y) (x - y) + (x + y)
= x + y
b) 3x2 + 3y2 - 6xy - 12
= 3 (x2 + y2 - 2xy - 4)
= 3 [(x2 - 2xy + y2) - 4]
= 3 [(x - y)2 - 22]
= 3 (x - y + 2) (x - y - 2)
(sai thì thôi)
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a: \(=\left(x+2-y\right)\left(x+2+y\right)\)
c: \(=\left(x-y\right)^2\)
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a. \(x^2-y^2=\left(x-y\right)\left(x+y\right)\)
b. \(x^2-6xy+9y^2-36=\left(x-3y\right)^2-6^2=\left(x-3y-6\right)\left(x-3y+6\right)\)
a: \(x^2-y^2=\left(x-y\right)\left(x+y\right)\)
b: \(x^2-6xy+9y^2-36=\left(x-3y\right)^2-6^2=\left(x-3y-6\right)\left(x-3y+6\right)\)
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a) Ta có: \(x^2y^2-x^2+6xy-9y^2\)
\(=x^2y^2-\left(x^2-6xy+y^2\right)\)
\(=\left(xy\right)^2-\left(x-3y\right)^2\)
\(=\left(xy-x+3y\right)\left(xy+x-3y\right)\)
b) Ta có: \(9-x^2+2xy-y^2\)
\(=9-\left(x^2-2xy+y^2\right)\)
\(=9-\left(x-y\right)^2\)
\(=\left(9-x+y\right)\left(9+x-y\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(5x^2-6xy+y^2=\left(9x^2-6xy+y^2\right)-4x^2=\left(3x-y\right)^2-4x^2=\left(3x-y-2x\right)\left(3x-y+2x\right)=\left(x-y\right)\left(5x-y\right)\)
\(5x^2-6xy+y^2\)
\(=5x^2-5xy-xy+y^2\)
\(=5x\left(x-y\right)-y\left(x-y\right)\)
\(=\left(x-y\right)\left(5x-y\right)\)
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a)\(=3x\left(x+2y\right)\)
c)\(=\left(x-7\right)\left(x-1\right)\)
b)\(=x\left(x-2y\right)+3\left(x-2y\right)=\left(x+3\right)\left(x-2y\right)\)
d)\(=\left(2x\right)^2-y^2=\left(2x-y\right)\left(2x+y\right)\)
\(a,3x^2+6xy=3x\left(x+2y\right)\\ c,x^2-8x+7=\left(x^2-x\right)-\left(7x-7\right)=x\left(x-1\right)-7\left(x-1\right)=\left(x-1\right)\left(x-7\right)\\ b,x^2-2xy+3x-6y=\left(x^2+3x\right)-\left(2xy+6y\right)=x\left(x+3\right)-2y\left(x+3\right)=\left(x+3\right)\left(x-2y\right)\\ d,4x^2-y^2=\left(2x-y\right)\left(2x+y\right)\)
=(x2+6xy+9) -y2
= (x+3)2-y2
=(x+3-y)(x+3+y)
sai rồi vì (x2+6xy+9) ko có y2 nên ko thể có hằng đẳng thức được