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a.
\(\left(x-y\right)\left(x^3+x^2y+xy^2+y^3\right)-x^4+y^4=x^4+x^3y+x^2y^2+xy^3-x^3y-x^2y^2-xy^3-y^4-x^4+y^4\)
\(=\left(x^4-x^4\right)+\left(y^4-y^4\right)+\left(x^3y-x^3y\right)+\left(xy^3-xy^3\right)+\left(x^2y^2-x^2y^2\right)=0\)
b.
\(\left(2-x\right)\left(1+2x\right)+\left(1+x\right)-\left(x^4+x^3-5x^2-5\right)=2+4x-x-2x^2+1+x-x^4-x^3+5x^2+5\)
\(=-x^4-x^3+\left(5x^2-2x^2\right)+\left(4x-x+x\right)+\left(1+2+5\right)=-x^4-x^3+3x^2+4x+8\)
c.
\(\left(x^2-7\right)\left(x+2\right)-\left(2x-1\right)\left(x-14\right)+x\left(x^2-2x-22\right)+35=x^3+2x^2-7x-14-2x^2+28x+x-14+x^3-2x^2-22x+35\)
\(=\left(x^3+x^3\right)+\left(2x^2-2x^2\right)+\left(28x-22x-7x+x\right)+\left(35-14\right)=2x^3+21\)
Lời giải:
$H=(x^3-3x^2+3x-1)-(x^3+8)+3(x^2-16)$
$=x^3-3x^2+3x-1-x^3-8+3x^2-48$
$=(x^3-x^3)+(-3x^2+3x^2)+3x+(-1-8-48)$
$=3x-57=3.\frac{-1}{2}-57=\frac{-117}{2}$
1) \(\left(x+2\right)^3-\left(x+6\right)^2-\left(x+1\right)\left(x^2-x+1\right)\)
\(=x^3+3.x^2.2+3.x.2^2+2^3-\left(x^2+2.x.6+6^2\right)-\left(x^3+1\right)\)
\(=x^3+6x^2+12x+8-x^2-12x-36-x^3-1\)
\(=5x^2-29\)
2. \(\left(x-3\right)\left(x^2+3x+9\right)-\left(x+3\right)^2\)
\(=x^3-3^3-\left(x^2+2.x.3+3^2\right)\)
\(=x^3-27-x^2-6x-9\)
\(=x^3-x^2-6x-36\)
\(=x^3-2x^2+3x^2-6x-36\)
\(=x^2\left(x-2\right)+3x\left(x-2\right)-36\)
\(=x\left(x-2\right)\left(x+3\right)-36\)
3. \(\left(2x-1\right)^2+2x^2.\left(x-2\right)\left(x+3\right)^2\)
\(=4x^2-4x+1+2x^2\left(x-2\right)\left(x^2+6x+9\right)\)
\(=4x^2-4x+1+2x^2\left(x^3+6x^2+9x-2x^2-12x-18\right)\)
\(=4x^2-4x+1+2x^2\left(x^3+4x^2-3x-18\right)\)
\(=4x^2-4x+1+2x^5+8x^4-6x^3-36x^2\)
\(=2x^5+8x^4-6x^3-32x^2-4x+1\)
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P/s: Không chắc lắm