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\(A=x^2+4x-21-x^2-4x+5=-16\\ B=-2\left(4x^2+20x+25\right)-\left(1-16x^2\right)\\ B=-8x^2-40x-50-1+16x^2=8x^2-40x-51\\ C=x^2\left(x^2-16\right)-\left(x^4-1\right)=x^4-16x^2-x^4+1=1-16x^2\\ D=x^3+1-\left(x^3-1\right)=2\\ E=x^3-3x^2+3x-1-x^3+1-9x^2+1=-12x^2+3x+1\)
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1: Ta có: \(\left(x+3\right)\left(x^2-3x+9\right)-\left(x^3+54\right)\)
\(=x^3+27-x^3-54\)
=-27
2: Ta có: \(\left(2x+y\right)\left(4x^2-2xy+y^2\right)-\left(2x-y\right)\left(4x^2+2xy+y^2\right)\)
\(=8x^3+y^3-8x^3+y^3\)
\(=2y^3\)
\(1,=x^3+270-x^3-54=-27\\ 2,=8x^3+y^3-8x^3+y^3=2y^3\\ 3,=x^3-3x^2+3x-1-x^3-8+3x^2-48=3x-57\\ 4,=x^3-x-x^3-1=-x-1\\ 5,=8x^3-5\left(8x^3+1\right)=-32x^3-5\\ 6,=27+x^3-27=x^3\\ 7,làm.ở.câu.3\\ 8,=x^3-6x^2+12x-8+6x^2-12x+6-x^3-1+3x\\ =3x-3\)
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Bài 1:
\(a,=15x^4-12x^3+9x^2\\ b,=-15x^3y^2+25x^2y^2-5xy^3\\ c,=5x^3-15x^2-4x^2+12x=5x^3-19x^2+12x\\ d,=3x^3-9x^2y+xy^2-3y^3+5x^2y-15xy^2=3x^3-3y^3-4x^2y-14xy^2\)
Bài 2:
\(a,=x^2+4x-21-x^2-4x+5=-16\\ b,=x^2+16x+64-2x^2-12x+32+x^2-4x+4=100\\ c,=x^4-16x^2-x^4+1=1-16x^2\\ d,=x^3+1-x^3+1=2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bạn chú ý đăng lẻ câu hỏi! 1/
a/ \(=x^3-2x^5\)
b/\(=5x^2+5-x^3-x\)
c/ \(=x^3+3x^2-4x-2x^2-6x+8=x^3=x^2-10x+8\)
d/ \(=x^2-x^3+4x-2x+2x^2-8=3x^2-x^3+2x-8\)
e/ \(=x^4-x^2+2x^3-2x\)
f/ \(=\left(6x^2+x-2\right)\left(3-x\right)=17x^2+5x-6-6x^3\)
a) ( x - 1 )3 - 4x( x + 1 )( x - 1 ) + 3( x - 1 )( x2 + x + 1 )
= x3 - 3x2 + 3x - 1 - 4x( x2 - 1 ) + 3( x3 - 13 )
= x3 - 3x2 + 3x - 1 - 4x3 + 4x + 3x3 - 3
= ( x3 - 4x3 + 3x3 ) - 3x2 + ( 3x + 4x ) + ( -1 - 3 )
= -3x2 + 7x - 4
b) ( x - 1 )( x - 2 )( 1 + x + x2 )( 4 + 2x + x2 )
= [ ( x - 1 )( 1 + x + x2 ) ][ ( x - 2 )( 4 + 2x + x2 ) ]
= [ ( x - 1 )( x2 + x + 1 ) ][ ( x - 2 )( x2 + 2x + 4 ) ]
= ( x3 - 13 )( x3 - 23 )
= ( x3 - 1 )( x3 - 8 )
= x6 - 9x3 + 8
c) ( x - 1 )3 + 3( x - 1 )( x2 + x + 1 ) - 4x( x + 1 )( x - 1 )
= x3 - 3x2 + 3x - 1 + 3( x3 - 13 ) - 4x( x2 - 1 )
= x3 - 3x2 + 3x - 1 + 3x3 - 3 - 4x3 + 4x
= ( x3 + 3x3 - 4x3 ) - 3x2 + ( 3x + 4x ) + ( -1 - 3 )
= -3x2 + 7x - 4
a,\(\left(x-1\right)^3-4x\left(x+1\right)\left(x-1\right)+3\left(x-1\right)\left(x^2+x+1\right)\)
\(=x^3-3x^2+3x-1-4x\left(x^2-1\right)+3\left(x^3-1\right)\)
\(=x^3-3x^2+3x-1-4x^3+4x+3x^3-3\)
\(=-3x^2+7x-4\)
b,\(\left(x-1\right)\left(x-2\right)\left(1+x+x^2\right)\left(4+2x+x^2\right)\)
\(=\left[\left(x-1\right)\left(x^2+x+1\right)\right]\left[\left(x-2\right)\left(x^2+2x+4\right)\right]\)
\(=\left(x^3-1\right)\left(x^3-8\right)\)
\(=x^6-9x^3+8\)
c,\(\left(x-1\right)^3+3\left(x-1\right)\left(x^2+x+1\right)-4x\left(x+1\right)\left(x-1\right)\)
\(=x^3-3x^2+3x-1+3\left(x^3-1\right)-4\left(x^2-1\right)\)
\(=x^3-3x^2+3x-1+3x^3-3-4x^3+4x\)
\(=-3x^2+7x-4\)