Cho : A=\(3x^2y-3xy-xy^2-5\)
B=\(3xy^2-6xy+x^2y-6\)
a) Tính A+B
b) Tính C sao cho C+B=A
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Sửa đề: B=-2x^2+xy+2y^2-3-5x+2y
a: A+B+C
=x^2-3xy-y^2+2x-3y+1-2x^2+xy+2y^2-3-5x+2y+C
=-x^2-2xy+y^2-3x-y-2+3x^2+7y^2-4xy-6x+4y+5
=2x^2+8y^2-6xy-9x+3y+3
b: 7A-B-C-9
=7A-9-(x^2+9y^2-3xy-11x+6y+2)
=7x^2-7y^2-21xy+14x-21y+7-x^2-9y^2+3xy-11x-6y-2-9
=6x^2-16y^2-18xy+3x-27y-4
c) (xy-1).(xy+5)
= x2y2+5xy-xy-5
=x2y2+4xy-5
a) b) d) bạn có thể ghi rõ được ko
A+B = \(4x^2y^3+6xy-7+\left(-8-3xy-3x^2y^3\right)\)
A+B = \(4x^2y^3+6xy-7-8-3xy-3x^2y^3\text{=}x^2y^3-3xy-15\)
A-B = \(7x^2y^3+9xy+1\)
B-A = \(-7x^2y^3-9xy-1\)
Bài 2:
\(M=x^2-2xy+y^2=\left(x-y\right)^2=\left(-3\right)^2=9\)
\(N=x^2+y^2=\left(x-y\right)^2+2xy=9+2.10=29\)
\(P=x^3-3x^2y+3xy^2-y^3=\left(x-y\right)^3=\left(-3\right)^3=-27\)
\(Q=x^3-y^3=\left(x-y\right)^3+3xy\left(x-y\right)=\left(-3\right)^3+3.10.\left(-3\right)=-117\)
Bài 1:
a) \(A=x^2+2xy+y^2=\left(x+y\right)^2=\left(-1\right)^2=1\)
b) \(B=x^2+y^2=\left(x+y\right)^2-2xy=\left(-1\right)^2-2.\left(-12\right)=25\)
c) \(C=x^3+3x^2y+3xy^2+y^3=\left(x+y\right)^3=\left(-1\right)^3=-1\)
d) \(D=x^3+y^3=\left(x+y\right)^3-3xy\left(x+y\right)=\left(-1\right)^3-3.\left(-12\right).\left(-1\right)=-37\)
a: \(M=x^3+x^2-y^3+y^2+xy-3xy-95\)
\(=\left(x-y\right)^3+\left(x-y\right)^2-95\)
\(=7^3+7^2-95=297\)
b: \(N=3\left[\left(x+y\right)^2-2xy\right]-2\left(x+y\right)+6xy-100\)
\(=3\cdot\left(25-2xy\right)-10+6xy-100\)
=75-6xy-10+6xy-100
=-35
\(a)A+B=3x^2y-3xy-xy^2-5+3xy^2-6xy+x^2y-6\\ =\left(3x^2y+x^2y\right)+\left(-3xy-6xy\right)+\left(xy^2+3xy^2\right)+\left(-5-6\right)\\ =3x^2y-9xy+4xy^2-11\)
\(b)C+B=A\Rightarrow C=A-B=(3x^2y-3xy-xy^2-5)-(3xy^2-6xy+x^2y-6)\\ =3x^2y-3xy-xy^2-5-3xy^2+6xy-x^2y+6\\ =\left(3x^2y-x^2y\right)+\left(-3xy+6xy\right)+\left(xy^2-3xy^2\right)+\left(-5+6\right)\\ =2x^2y+3xy-2xy^2+1\)