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\(2x+2y+3xy\left(x+y\right)+5\left(x^3y^2+x^2y^3\right)+4=2\left(x+y\right)+3xy\left(x+y\right)+5x^2y^2\left(x+y\right)+4=2.0+3xy.0+5x^2y^2.0+4=4\)
\(2x+2y+3xy\left(x+y\right)+5\left(x^3y^2+x^2y^3\right)+4\)
\(=2\left(x+y\right)+3xy\left(x+y\right)+5\left(xy\right)^2\cdot\left(x+y\right)+4\)
=4
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\(A=x^3-y^3-21xy\)
\(A=\left(x-y\right).\left(x^2+xy+y^2\right)-21xy\)
\(A=7.\left(x^2+xy+y^2\right)-21xy\)
\(A=7.\left(x^2+xy+y^2+3xy\right)\)
\(A=7.\left(x^2+2xy+y^2+2xy\right)\)
\(A=7.\text{[}\left(x+y\right)^2+2xy\text{]}\)
\(A=7.\left(7^2+2xy\right)\)
\(A=7^3+14xy\)
Ngáo rồi @@
\(\)
\(A=x^3-y^3-21xy\)
\(\Rightarrow A=\left(x-y\right)\left(x^2+xy+y^2\right)-21xy\)
\(\Rightarrow A=7\left(x^2+xy+y^2\right)-21xy\)
\(\Rightarrow A=7\left(x^2+xy+y^2-3xy\right)\)
\(\Rightarrow A=7\left(x^2+y^2-2xy\right)\)
\(\Rightarrow A=7\left(x-y\right)^2\)
\(\Rightarrow A=7.7^2\)
\(\Rightarrow A=7.49\)
\(\Rightarrow A=343\)
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a: \(A=2\left(x+y\right)+3xy\left(x+y\right)+5x^2y^2\left(x+y\right)=0\)
b: \(B=3xy\left(x+y\right)+2x^2y\left(x+y\right)=0\)
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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: \(\left(-\dfrac{1}{4}x^2y\right)^2\cdot\left(\dfrac{2}{3}xy^4\right)^3\)
\(=\dfrac{1}{16}x^4y^2\cdot\dfrac{8}{27}x^3y^{12}\)
\(=\dfrac{1}{54}x^7y^{14}\)
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a, Thay x = 1/2 ; y = -1/3 ta được
\(A=\dfrac{3.1}{8}\left(-\dfrac{1}{3}\right)+\dfrac{6.1}{4}.\left(\dfrac{1}{9}\right)+\dfrac{3.1}{2}\left(-\dfrac{1}{3}\right)^3\)
\(=-\dfrac{1}{8}+\dfrac{1}{12}+\dfrac{3}{2\left(-27\right)}=-\dfrac{7}{72}\)
b, Thay x = -1 ; y = 3 ta được
\(B=9+\left(-1\right).3-1+27=32\)
bạn thay chỗ nào x là \(\dfrac{1}{2}\) còn chỗ nào y là \(\dfrac{-1}{3}\)nhé
còn như là 3\(x^3\)y thì thành là 3.\(x^3\).y nhé
mk lười nên ko giải ra cho bạn được
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a. A = (a + b)3 + (a - b)3
A = (a + b + a - b)\(\left[\left(a+b\right)^2-\left(a+b\right)\left(a-b\right)+\left(a-b\right)^2\right]\)
A = 2a\(\left[\left(a^2+2ab+b^2\right)-\left(a^2-b^2\right)+\left(a^2-2ab+b^2\right)\right]\)
A = 2a(a2 + 2ab + b2 - a2 + b2 + a2 - 2ab + b2)
A = 2a(a2 + 3b2)
A = 2a3 + 3ab2
\(VP=\left(x-y\right)^3+3xy\left(x-y\right)\)
\(=x^3-3x^2y+3xy^2-y^3+3xy\left(x-y\right)\)
\(=x^3-3xy\left(x-y\right)-y^3+3xy\left(x-y\right)\)
\(=x^3-y^3=VT\left(đpcm\right)\)
Biến đổi VP ta có:
\(\left(x-y\right)^3+3xy\left(x-y\right)\)
\(=x^3-y^3-3xy\left(x-y\right)+3xy\left(x-y\right)\)
\(=x^3-y^3\)
Vậy ....