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#)Giải :
\(x^3-2x-4\)
\(=x^3+2x^2-2x^2+2x-4x-4\)
\(=x^3+2x^2+2x-2x^2-4x-4\)
\(=x\left(x^2+2x+2\right)-2\left(x^2+2x+2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
\(x^4+2x^3+5x^2+4x-12\)
\(=x^4+x^3+6x^2+x^3+x^2+6x-2x^2-2x-12\)
\(=x^2\left(x^2+x+6\right)+x\left(x^2+x+6\right)-2\left(x^2+x+6\right)\)
\(=\left(x^2+x+6\right)\left(x^2+x-2\right)\)
\(=\left(x^2+x+6\right)\left(x-1\right)\left(x+2\right)\)
Câu 1.
Đoán được nghiệm là 2.Ta giải như sau:
\(x^3-2x-4\)
\(=x^3-2x^2+2x^2-4x+2x-4\)
\(=x^2\left(x-2\right)+2x\left(x-2\right)+2\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
A,
x^2 - y^2 -2x -2y
= (x^2 - y^2) -(2x +2y)
= (x+y)(x-y) -2(x+y)
= (x+y)(x-y-2)
B,
5x^6 - 320
=5(x^6 - 64)
=5( (x^3)^2 - 8^2)
= 5( x^3 - 8)(x^3+8)
=5(x-2)(x^2 + 2x+4)(x+2)(x^2-2x-4)
\(\left(x^2+4x-3\right)^2-5x.\left(x^2+4x-3\right)+6x^2\)
\(=\left[\left(x^2+4x-3\right)^2-2.\left(x^2+4x-3\right).2,5x+\left(2,5x\right)^2\right]-\left(0,5x\right)^2\)
\(=\left(x^2+4x-3-2,5x\right)^2-\left(0,5x\right)^2\)
\(=\left(x^2+4x-3-2,5x-0,5x\right).\left(x^2-4x-3-2,5x+0,5x\right)\)
\(=\left(x^2+x-3\right).\left(x^2+2x-3\right)\)
Tham khảo nhé~
A = 6x4 - 5x3 + 4x2 + 2x - 1
= 6x4 + 3x3 - 8x3 - 4x2 + 8x2 + 4x - 2x - 1
= 3x3. ( 2x + 1 ) - 4x2 ( 2x + 1 ) + 4x ( 2x + 1 ) - ( 2x + 1 )
= ( 2x + 1 ) ( 3x3 - 4x2 + 4x - 1 )
= ( 2x + 1 ) ( 3x3 - x2 - 3x2 + x + 3x - 1 )
= ( 2x + 1 ) [ x2 ( 3x - 1 ) - x ( 3x - 1 ) + ( 3x - 1 ) ]
= ( 2x + 1 ) ( 3x - 1 ) ( x2 - x + 1 )
B = 4x4 + 4x3 + 5x2 + 8x - 6
= 4x4 - 2x3 + 6x3 - 3x2 + 8x2 - 4x + 12x - 6
= 2x3 ( 2x - 1 ) + 3x2 ( 2x - 1 ) + 4x ( 2x - 1 ) + 6 ( 2x - 1 )
= ( 2x - 1 ) ( 2x3 + 3x2 + 4x + 6 )
= ( 2x - 1 ) [ x2 ( 2x + 3 ) + 2 ( 2x + 3 ) ]
= ( 2x - 1 ) ( 2x + 3 ) ( x2 + 2 )
C = x4 + x3 - 5x2 + x - 6
= x4 - 2x3 + 3x3 - 6x2 + x2 - 2x + 3x - 6
= x3 ( x - 2 ) + 3x2 ( x - 2 ) + x ( x - 2 ) + 3 ( x - 2 )
= ( x - 2 ) ( x3 + 3x2 + x + 3 )
= ( x - 2 ) [ x2 ( x + 3 ) + ( x + 3 ) ]
= ( x - 2 ) ( x + 3 ) ( x2 + 1 )
5x2 - 5xy + 4y - 4x
= 5x ( x - y ) - 4 ( x - y )
= ( 5x - 4 ) ( x - y )
( x + y )3 + ( x - y )3
= 2x3 + 6xy2
= 2x ( x2 + 3y2 )
5 x^2 - 5xy + 4y - 4x
= 5x ( x - y ) - 4 ( x - y )
= ( x - y ) ( 5x - 4 )
( x + y )^3 + ( x - y )^3
= \(x^3+3x^2y+3xy^2+y^3+x^3-3x^2y+3xy^2-y^3\)
= \(2x^3+6xy^2\)
=\(2x\left(x^2+3y^2\right)\)
a) \(x^2+5x-6=x^2-x+6x-6=x.\left(x-1\right)+6.\left(x-1\right)=\left(x+6\right)\left(x-1\right)\)
b) \(7x-6x^2-2=3x-6x^2-2+4x=3x.\left(1-2x\right)-2.\left(1-2x\right)=\left(1-2x\right)\left(3x-2\right)\)
c)\(x^2+4x+3=x^2+x+3x+3=x.\left(x+1\right)+3.\left(x+1\right)=\left(x+3\right)\left(x+1\right)\)
d) \(2x^2+5x-3=2x^2-x+6x-3=x.\left(2x-1\right)+3.\left(2x-1\right)=\left(x+3\right)\left(2x-1\right)\)
\(x^3+4x^2+5x+2\)
\(=x^3+2x^2+2x^2+4x+x+2\)
\(=x^2\left(x+2\right)+2x\left(x+2\right)+\left(x+2\right)\)
\(=\left(x+2\right)\left(x^2+2x+1\right)\)
\(=\left(x+2\right)\left(x+1\right)^2\)
Có : x^3+4x^2+5x+2
= (x^3+x^2)+(3x^2+3x)+(2x+2)
= (x+1).(x^2+3x+2)
= (x+1).[(x^2+x)+(2x+2)]
= (x+1).(x+1).(x+2)
= (x+1)^2.(x+2)
Tk mk nha