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`Answer:`
\(A+\left(6x^2y+2xy+4y\right)=7x^2y-y\)
\(\Leftrightarrow A=\left(7x^2y-y\right)-\left(6x^2y+2xy+4y\right)\)
\(\Leftrightarrow A=\left(7x^2y-6x^2y\right)+\left(-y-4y\right)-2xy\)
\(\Leftrightarrow A=x^2y-5y-2xy\)
\(A+\left(6x^2y+2xy+4y\right)=7x^2y-y\)
\(A=7x^2y-y-\left(6x^2y+2xy+4y\right)\)
\(A=7x^2y-y-6x^2y-2xy-4y\)
\(A=\left(7x^2y-6x^2y\right)+\left(-y-4y\right)-2xy\)
\(A=x^2y-5y-2xy\)
A+6x^2y+2xy+4y=7x^2y-y
A=7x^2y-y-6x^2y-2xy-4y
A=x^2y-5y-2xy
A=x^2y-5y-2xy
Bài 2 :
a, \(A+B=x^2-2y^2+xy+1+x^2+y^2-x^2y^2-1=2x^2-y^2+xy-x^2y^2\)
b, \(C+A+B=2x^2-y^2+xy-x^2y^2+2x^2-y^2+xy-x^2y^2=4x^2-2y^2+2xy-2x^2y^2\)
bạn đăng tách bài ra cho mọi người cùng giúp nhé
Bài 1 :
a, \(6x^2-3xy^2+M=x^2+y^2-2xy^2\Leftrightarrow M=-5x^2+y^2+xy^2\)
b, \(N-\left(2xy-4y^2\right)=5xy+x^2-7y^2\)
\(\Leftrightarrow N=5xy+x^2-7y^2+2xy-4y^2=x^2+7xy-11y^2\)
a) Ta có : 6x2−3xy2+M=x2+y2−2xy26x2−3xy2+M=x2+y2−2xy2
=> M=(x2+y2−2xy2)−(6x2−3xy2)M=(x2+y2−2xy2)−(6x2−3xy2)
⇒M=−5x2+xy2+y2⇒M=−5x2+xy2+y2
Vậy đa thức M=−5x2+xy2+y2M=−5x2+xy2+y2
b) Ta có : M−(2xy−4y2)=5xy+x2−7y2M−(2xy−4y2)=5xy+x2−7y2
=> M=5xy+x2−7y2+(2xy−4y2)M=5xy+x2−7y2+(2xy−4y2)
=> M=x2+7xy−11y2
a, \(A=-x^2+4xy^2-2xz+3y^2\)
b, \(B=6x^2+9xy-y^2-5x^2+2xy=x^2+11xy-y^2\)
c, \(A=3xy-4y^2-x^2+7xy-8y^2=-x^2+10xy-12y^2\)
Ta có: \(M=x^2+y^2-2xy^2-6x^2-3xy^2\)
\(\Rightarrow M=-5x^2+y^2-5xy^2\)
\(M=6x^2+9xy-y^2-5x^2+2xy\)
\(M=x^2+11xy-y^2\)
\(N=3xy-4y^2-x^2+7xy-8y^2\)
\(N=-x^2+10xy-12y^2\)
a. \(M+\left(5x^2-2xy\right)=6x^2+9xy-y^2\)
\(\Rightarrow M=6x^2+9xy-y^2-5x^2+2xy\)
b. \(\left(3xy-4y^2\right)-N=x^2-7xy+8y^2\)
\(\Rightarrow N=3xy-4y^2-x^2+7xy-8y^2\)
Bài 2:
C=A-B
\(=2x^2-6xy+4y^2+5x^2-4xy-7y^2\)
\(=7x^2-10xy-3y^2\)
\(=7\cdot1^2-10\cdot1\cdot\dfrac{1}{2}-3\cdot\dfrac{1}{4}=7-5-\dfrac{3}{4}=2-\dfrac{3}{4}=\dfrac{5}{4}\)