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1/ phân tích thành nhân tử ;
= C2-( a +b )2=( c-a -b ) . ( c+a +b )
a) \(x^2-10x+9\)
\(=x^2-9x-x+9\)
\(=x\left(x-9\right)-\left(x-9\right)\)
\(=\left(x-1\right)\left(x-9\right)\)
b) \(3x^2-10xy+3y^2\)
\(=3x^2-9xy-xy+3y^2\)
\(=3x\left(x-3y\right)-y\left(x-3y\right)\)
\(=\left(3x-y\right)\left(x-3y\right)\)
a) x2 + 7x + 12 = x2 + 3x + 4x + 12 = x( x + 3 ) + 4( x + 3 ) = ( x + 3 )( x + 4 )
b) x2 - 10x + 16 = x2 - 2x - 8x + 16 = x( x - 2 ) - 8( x - 2 ) = ( x - 2 )( x - 8 )
c) x2 + 6x + 8 = x2 + 2x + 4x + 8 = x( x + 2 ) + 4( x + 2 ) = ( x + 2 )( x + 4 )
d) x2 - 8x + 15 = x2 - 3x - 5x + 15 = x( x - 3 ) - 5( x - 3 ) = ( x - 3 )( x - 5 )
e) x2 - 8x - 9 = x2 + x - 9x - 9 = x( x + 1 ) - 9( x + 1 ) = ( x + 1 )( x - 9 )
f) x2 + 14x + 48 = x2 + 6x + 8x + 48 = x( x + 6 ) + 8( x + 6 ) = ( x + 6 )( x + 8 )
a) 5x2 - 10x = 5x( x - 2 )
b) x2 - y2 - 2x + 2y = (x2 - y2) - (2x - 2y)
= (x - y ) ( x + y)-2 (x-y)
= ( x - y) ( x + y - 2)
c) 4x2 - 4xy - 8y2 = (4x2 - 4xy + 8y2) - 9y2
= (2x - 9y2) - 3y2
= (2x - y - 3y) (2x - y + 3y)
= (2x - 4y) (2x + 2y)
= 4(x - 2y) (x + y)
a) 5x2 - 10x = 5x( x - 2 )
b) x2 - y2 - 2x + 2y = (x2 - y2) - (2x - 2y)
= (x - y ) ( x + y)-2 (x-y)
= ( x - y) ( x + y - 2)
c) 4x2 - 4xy - 8y2 = (4x2 - 4xy + 8y2) - 9y2
= (2x - 9y2) - 3y2
= (2x - y - 3y) (2x - y + 3y)
= (2x - 4y) (2x + 2y)
= 4(x - 2y) (x + y)
\(x^2-10x+16=x^2-8x-2x+16=x\left(x-8\right)-2\left(x-8\right)=\left(x-8\right)\left(x-2\right)\)
\(x^2-2x-15=x^2-5x+3x-15=x\left(x-5\right)+3\left(x-5\right)=\left(x-5\right)\left(x+3\right)\)
\(2x^2+7x+3=2x^2+x+6x+3=x\left(2x+1\right)+3\left(2x+1\right)=\left(x+3\right)\left(2x+1\right)\)
a) \(x^2-10x+16=x^2-8x-2x+16=\left(x^2-8x\right)-\left(2x-16\right)=x\left(x-8\right)-2\left(x-8\right)=\left(x-8\right)\left(x-2\right)\)b) \(x^2-2x-15=x^2+3x-5x-15=\left(x^2+3x\right)-\left(5x+15\right)=x\left(x+3\right)-5\left(x+3\right)=\left(x+3\right)\left(x-5\right)\)c) \(2x^2+7x+3=2x^2+x+6x+3=\left(2x^2+x\right)+\left(6x+3\right)=x\left(2x+1\right)+3\left(2x+1\right)=\left(2x+1\right)\left(x+3\right)\)
c ) =x2-x-9x+9
=x(x-1)-9(x-1)
=(x-1)(x-9)