a, \(\left(25y^2+\dfrac{1}{9}x^2+\dfrac{5}{3}xy\right)\left(5y-\dfrac{1}{3}x\right)\)
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b, \(-125y^3-\dfrac{1}{27}x^3\)
\(=\left(-5y\right)^3-\left(\dfrac{1}{3}x\right)^3\)
\(=\left(-5y-\dfrac{1}{3}x\right)\left(25y^2-\dfrac{5}{3}xy+\dfrac{1}{9}x^2\right)\)
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Câu a :
\(\left(25y^2+\dfrac{1}{9}x^2+\dfrac{5}{3}xy\right)\left(5y-\dfrac{1}{3}x\right)\)
\(=\left(5y+\dfrac{1}{3}x\right)^2\left(5y-\dfrac{1}{3}x\right)\)
Câu b :
\(-125y^3-\dfrac{1}{27}x^3\)
\(=\left(-5y\right)^3-\left(\dfrac{1}{3}x\right)^3\)
\(=\left(-5y-\dfrac{1}{3}x\right)\left(25y^2+\dfrac{5}{3}xy+\dfrac{1}{9}x^2\right)\)
a) (25y2+1/9x2+5/3xy)(5y-1/3x)=(5y+1/3x)2.(5y-1/3x)
b) -125y3-1/27x3= -(125y3+1/27x3)= -(5x+1/3y)(25x2-5/3xy+1/9y2)