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a/ 9x2-12xy+4y2 = (3x - 2y)2
b/ 25x2-10x+1 = (5x - 1)2
c/ 9x2-12x+4 = (3x - 2)2
d/ 4x2+20x+25 = (2x + 5)2
e/ x4-4x2+4 = (x2 - 2)2
a, \(25x^2+5xy+\frac{1}{4}y^2=\left(5x\right)^2+2.5x.\frac{1}{2}y+\left(\frac{1}{2}y\right)^2\)
\(=\left(5x+\frac{1}{2}y\right)^2\)
b, \(9x^2+12x+4=\left(3x\right)^2+2.3x.2+2^2=\left(3x+2\right)^2\)
c, \(x^2-6x+5-y^2-4y=\left(x^2-6x+9\right)-\left(y^2+4y+4\right)\)
\(=\left(x-3\right)^2-\left(y+2\right)^2=\left(x-y-5\right)\left(x+y-1\right)\)
d, \(\left(2x-y\right)^2+4\left(x+y\right)^2-4\left(2x-y\right)\left(x+y\right)\)
\(=\left(2x-y\right)^2-2\left(2x-y\right)\left(2x+2y\right)+\left(2x+2y\right)^2\)
\(=\left(2x-y+2x+2y\right)^2=\left(4x+y\right)^2\)
a) ( 2x + 1 )2 + 10( 2x + 1 ) + 25
= ( 2x + 1 )2 + 2.( 2x + 1 ).5 + 52
= [ ( 2x + 1 ) + 5 ]2
= ( 2x + 1 + 5 )2
= ( 2x + 6 )2
b) x2 + 2x( y - 2 ) + y2 - 4y + 4
= x2 + 2x( y - 2 ) + ( y2 - 4y + 4 )
= x2 + 2x( y - 2 ) + ( y - 2 )2
= [ x + ( y - 2 ) ]2
= ( x + y - 2 )2
c) x2 + 12x + 40 + y2 + 4y
= ( x2 + 12x + 36 ) + ( y2 + 4y + 4 )
= ( x + 6 )2 + ( y + 2 )2 ( cấy ni không viết được ;-; )
d) x2 - 8x - 20 - y2 - 12y
= ( x2 - 8x + 16 ) - ( y2 + 12y + 36 )
= ( x - 4 )2 - ( y + 6 )2
= [ ( x - 4 ) - ( y + 6 ) ][ ( x - 4 ) + ( y + 6 ) ]
= ( x - 4 - y - 6 )( x - 4 + y + 6 )
= ( x - y - 10 )( x + y + 2 )
e) x2 + y2 + 4x + 4y + 2( x + 2 )( y + 2 ) + 8
= ( x2 + 4x + 4 ) + 2( x + 2 )( y + 2 ) + ( y2 + 4y + 4 )
= ( x + 2 )2 + 2( x + 2 )( y + 2 ) + ( y + 2 )2
= [ ( x + 2 ) + ( y + 2 ) ]2
= ( x + 2 + y + 2 )2
= ( x + y + 4 )2
1. \(x^2-2x+2+4y^2+4y\)
\(=\left(x^2-2x+1\right)+\left(4y^2+4y+1\right)\)
\(=\left(x-1\right)^2+\left(2y+1\right)^2\)
2. \(4x^2-4x+y^2+2y+2\)
\(=\left(4x^2-4x+1\right)+\left(y^2+2y+1\right)\)
\(=\left(2x-1\right)^2+\left(y+1\right)^2\)
3. \(4x^2+4x+4y^2+4y+2\)
\(=\left(4x^2+4x+1\right)+\left(4y^2+4y+1\right)\)
\(=\left(2x+1\right)^2+\left(2y+1\right)^2\)
4. \(4x^2+y^2+12x+4y+13\)
\(=\left(4x^2+12x+9\right)+\left(y^2+4y+4\right)\)
\(=\left(2x+3\right)^2+\left(y+2\right)^2\)
\(x^2-2x+2+4y^2+4y\)
\(=\left(x^2-2x+1\right)+\left(4y^2+4y+1\right)\)
\(=\left(x-1\right)^2+\left(2y+1\right)^2\)
\(4x^2-4x+y^2+2y+2\)
\(=\left(2x-1\right)^2+\left(y+1\right)^2\)
a) \(x^2-6x+9=x^2-2\cdot x\cdot3+3^2=\left(x-3\right)^2\)
b) \(4x^2-12xy+9y^2=\left(2x\right)^2-2\cdot2x\cdot3y+\left(3y\right)^2=\left(2x-3y\right)^2\)
c) \(4x^2-2x+1=\left(2x-1\right)^2\)
d) \(x^2+8xy+16y^2=\left(x+4y\right)^2\)
a. \(9x^2+25-12xy+5y^2-10y\)
\(=\left(9x^2-12xy+4y^2\right)+\left(25+y^2-10y\right)\)
\(=9\left(x^2-\frac{4xy}{3}+\frac{4y^2}{9}\right)+\left(5-y\right)^2\)
\(=9\left(x-\frac{2y}{3}\right)^2+\left(5-y\right)^2\)
1a/ z2 - 6z + 5 - t2 - 4t = z2 - 2 . 3z + 32 - 4 - t2 - 4t = (z2 - 2 . 3z + 32) - (22 + 2 . 2t + t2) = (z - 3)2 - (2 + t)2
b/ x2 - 2xy + 2y2 + 2y2 + 1 = x2 - 2xy + y2 + y2 + 2y + 1 = (x2 - 2xy + y2) + (y2 + 2y + 1) = (x - y)2 + (y + 1)2
c/ 4x2 - 12x - y2 + 2y + 8 = (2x)2 - 12x - y2 + 2y + 32 - 1 = [ (2x)2 - 2 . 3 . 2x + 32 ] - (y2 - 2y + 1) = (2x - 3)2 - (y - 1)2
2a/ (x + y + 4)(x + y - 4) = x2 + xy - 4x + xy + y2 - 4y + 4x + 4y + 16 = x2 + (xy + xy) + (-4x + 4x) + (-4y + 4y) + y2 + 16
= x2 + 2xy + y2 + 42 = (x + y)2 + 42
b/ (x - y + 6)(x + y - 6) = x2 + xy - 6x - xy - y2 + 6y + 6x + 6y - 36 = x2 + (xy - xy) + (-6x + 6x) + (6y + 6y) - y2 - 36
= x2 - y2 + 12y - 62 = x2 - (y2 - 12y + 62) = x2 - (y2 - 2 . 6y + 62) = x2 - (y - 6)2
c/ (y + 2z - 3)(y - 2z - 3) = y2 -2yz - 3y + 2yz - 4z2 - 6z - 3y + 6z + 9 = y2 + (-2yz + 2yz) + (-3y - 3y) + (-6z + 6z) - 4z2 + 9
= y2 - 6y - 4z2 + 9 = (y2 - 6y + 9) - 4z2 = (y - 3)2 - (2z)2
d/ (x + 2y + 3z)(2y + 3z - x) = 2xy + 3xz - x2 + 4y2 + 6yz - 2xy + 6yz + 9z2 - 3xz = (2xy - 2xy) + (3xz - 3xz) - x2 + (6yz + 6yz) + 9z2 + 4y2
= -x2 + 4y2 + 12yz + 9z2 = (4y2 + 12yz + 9z2) - x2 = [ (2y)2 + 2 . 2 . 3yz + (3z)2 ] - x2 = (2y + 3z)2 - x2
\(a.=\left(2x\right)^2-2.2x.2y+\left(2y\right)^2=\left(2x-2y\right)^2\)
\(b.=\left(3x\right)^2-2.3x.2+2^2=\left(3x-2\right)^2\)
a. 4x2+4y2-8xy=(2x)2+(2y)2-8xy
=(2x-2y)2
b.9x2-12x+4=(3x)2-12x+22
=(3x-2)2
c.xy2+1/4x2y4+1=xy2+(1/2xy2)2+1
=(1/2xy2+2)2