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\(C=5x^3y^2-4x^3y^2+3x^2y^3+\dfrac{1}{2}x^2y^3+\dfrac{1}{3}x^4y^5-3x^4y^5-\dfrac{1}{7}\)
\(=x^3y^2+\dfrac{7}{2}x^2y^3-\dfrac{8}{3}x^4y^5-\dfrac{1}{7}\)
B=-4x^5y+x^4y^3-3x^2y^3z^2+4x^5y-2y^4-x^4y-x^4y+3y^4+4y^2x^2z^2-y^4+\(\frac{1}{2}\)
=(-4x^5y+4x^5y)+x^4y^3-3x^2y^3z^2+(2y^4+3y^4-y^4)+(-x^4y-x^4y)+4y^2x^2z^2+\(\frac{1}{2}\)
=x^4y^3-3y^3z^2-2x^4y+4y^2x^2z^2+\(\frac{1}{2}\)
1) Ta có: \(\dfrac{1}{7}x^2y^3\cdot\left(-\dfrac{14}{3}xy^2\right)\cdot\left(-\dfrac{1}{2}xy\right)\left(x^2y^4\right)\)
\(=\left(-\dfrac{1}{7}\cdot\dfrac{14}{3}\cdot\dfrac{-1}{2}\right)\left(x^2y^3\cdot xy^2\cdot xy\cdot x^2y^4\right)\)
\(=\dfrac{1}{3}x^6y^{10}\)
2) Ta có: \(\left(3xy\right)^2\cdot\left(-\dfrac{1}{2}x^3y^2\right)\)
\(=9xy^2\cdot\dfrac{-1}{2}x^3y^2\)
\(=-\dfrac{9}{2}x^4y^4\)
3) Ta có: \(\left(-\dfrac{1}{4}x^2y\right)^2\cdot\left(\dfrac{2}{3}xy^4\right)^3\)
\(=\dfrac{1}{16}x^4y^2\cdot\dfrac{8}{27}x^3y^{12}\)
\(=\dfrac{1}{54}x^7y^{14}\)
Ta có
4 x 2 y − 2 x y 2 + 1 3 x 2 y − x + 2 x 2 y + x y 2 − 1 3 x − 6 x 2 y = 4 x 2 y + 1 3 x 2 y + 2 x 2 y − 6 x 2 y + − 2 x y 2 + x y 2 + − 1 3 x − x = 1 3 x 2 y − x y 2 − 4 3 x
Chọn đáp án B