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a) \(9x^2-16\)
\(=\left(3x\right)^2-4^2\)
\(=\left(3x-4\right)\left(3x+4\right)\)
b) \(x^2+4xy+4y^2-3x-6y\)
\(=\left(x^2+4xy+4y^2\right)-\left(3x+6y\right)\)
\(=\left[x^2+2\cdot x\cdot2y+\left(2y\right)^2\right]-3\left(x+2y\right)\)
\(=\left(x+2y\right)^2-3\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x+2y-3\right)\)
#\(Toru\)
\(a.3x^2-12xy=3x\left(x-4y\right)\)
\(b.x^2+7x-2\left(x+7\right)=x\left(x+7\right)-2\left(x+7\right)=\left(x-2\right)\left(x+7\right)\)
\(c.8x^3-8x^2+2x=2x\left(4x^2-4+1\right)=2x\left(2x-1\right)^2\)
\(d.x^2-y^2+12y-36=x^2-\left(y-6\right)^2=\left(x-y-6\right)\left(x-y+6\right)\)
Bài làm
a) 3x2 - 12xy
= 3x( x - 4y )
b) x2 + 7x - 2( x + 7 )
= x( x + 7 ) - 2( x + 7 )
= ( x + 7 )( x - 2 )
c) 8x3 - 8x2 + 2x
= 2x( 4x2 - 4x + 1 )
= 2x( 2x - 1 )2
d) x2 - y2 + 12y - 36
= x2 - ( y2 - 12y + 36 )
= x2 - ( y2 - 2.y.6 + 62 )
= x2 - ( y - 6 )2
= ( x - y + 6 )( x + y - 6 )
# Học tốt #
\(y^2-12y+36-144x^2=\left(y-6\right)^2-\left(12x\right)^2=\left(y-12x-6\right)\left(y+12x-6\right)\)
\(=\left(y^2-12y+36\right)-144x^2=\left(y-6\right)^2-144x^2=\left(y-12x-6\right)\left(y+12x-6\right)\)
\(12y-9x^2+36-3x^2y\)
\(=\left(36-9x^2\right)-\left(3x^2y-12y\right)\)
\(=-9\left(x^2-4\right)-3y\left(x^2-4\right)\)
\(=\left(-3\right)\left(x-2\right)\left(x+2\right)\left(3+y\right)\)
Ta có: 9 x 2 - 1 = ( 3 x ) 2 - 1 2 = ( 3 x - 1 ) ( 3 x + 1 )
Ta có: 9 x 2 - 1 = ( 3 x ) 2 - 1 2 = ( 3 x - 1 ) ( 3 x + 1 )
\(x^2+4y^2+9-4xy-6x+12y\)
\(=\left(x^2-4xy+4y^2\right)+\left(-6x+12y\right)+9\)
\(=\left(x-2y\right)^2-6\left(x-2y\right)+9\)
\(=\left(x-2y-3\right)^2\)
a) \(=\left(a+2c\right)^2-16=\left(a+2c-4\right)\left(a+2c+4\right)\)
b) \(=3y\left(4-x^2\right)+9\left(4-x^2\right)=3\left(4-x^2\right)\left(y+3\right)\)
\(=3\left(2-x\right)\left(2+x\right)\left(y+3\right)\)
a, a2 + 4ac + 4c2 - 16 = (a + 2c)2 - 42 = (a + 2c -4).(a + 2c +4)
b, 12y - 9x2 + 36 - 3x2y = (12y + 36) - (3x2y + 9x2) = 12.(y+ 3) - 3x2.(y + 3) =(y + 3).(12 - 3x2)