ô ri đúng 

TA CÓ: \(B-\left(x^2+xy+y^2\right)=2x^2-xy+y^2\)

\(\Rightarrow B=\left(2x^2-xy+y^2\right)+\left(x^2+xy+y^2\right)\)

\(B=2x^2-xy+y^2+x^2+xy+y^2\)

\(B=\left(2x^2+x^2\right)+\left(y^2+y^2\right)+\left(xy-xy\right)\)

\(B=3x^2+2y^2\)

TA CÓ: \(\left(\frac{1}{2}.xy+x^2-\frac{1}{2}x^2y\right)-C=-xy+x^2y+1\)

\(\Rightarrow C=\left(\frac{1}{2}xy+x^2-\frac{1}{2}x^2y\right)-\left(-xy+x^2y+1\right)\)

\(C=\frac{1}{2}xy+x^2-\frac{1}{2}x^2y+xy-x^2y-1\)

\(C=\left(\frac{1}{2}xy+xy\right)+\left(\frac{-1}{2}x^2y-x^2y\right)+x^2-1\)

\(C=\frac{3}{2}xy+\frac{-3}{2}x^2y+x^2-1\)

mk nha

Tìm đa thức B:

B - ( x² + xy + y² ) = 2x² - xy + y²

B = ( 2x² - xy + y² ) + ( x² + xy + y² )

B = ( 2x² + x² ) + ( - xy + xy ) + ( y² + y² )

B = 3x² + 2y²

Tìm đa thức C:

( \(\frac{1}{2}\). xy + x² - \(\frac{1}{2}\)x²y ) - C = - xy + x²y + 1

C = ( \(\frac{1}{2}\). xy + x² - \(\frac{1}{2}\)x²y ) - ( - xy + x²y + 1 )

C = \(\frac{1}{2}\). xy + x² - \(\frac{1}{2}\)x²y + xy - x²y + 1

C =(  \(\frac{1}{2}\)xy + xy ) + ( - \(\frac{1}{2}\)x²y - x²y ) + x² + 1

C = -1 ,5x²y + x² + 1

CHỈ GỢI Ý THÔI 

M = (x^2 - xy) + (xy^2 - y^3) - x - y^2 + 5

M = x(x - y) + y^2(x - y) - x - y^2 + 5 

.....

PHẦN N KO BIẾT LÀM

:/

\(P+R=-xy\cdot(x-y)\\\Leftrightarrow R=-xy(x-y)-P\\\Leftrightarrow R=-x^2y+xy^2-(5x^2y-2xy^2+xy-x+y-2)\\\Leftrightarrow R=-x^2y+xy^2-5x^2y+2xy^2-xy+x-y+2\\\Leftrightarrow R=(-x^2y-5x^2y)+(xy^2+2xy^2)-xy+x-y+2\\\Leftrightarrow R=-6x^2y+3xy^2-xy+x-y+2\)

Ta có:

\(P+R=-xy\cdot\left(x-y\right)\)

\(\Leftrightarrow\left(5x^2y-2xy^2+xy-x+y-2\right)+R=-x^2y+xy^2\)

\(\Leftrightarrow R=-x^2y+xy^2-5x^2y+2xy^2+xy+x-y+2\)

\(\Leftrightarrow R=\left(-x^2y-5x^2y\right)+\left(xy^2+2xy^2\right)+xy+x-y+2\)

\(\Leftrightarrow R=-6x^2y+3xy^2+xy+x-y+2\)

2:

a: A(x)=0

=>5x-10-2x-6=0

=>3x-16=0

=>x=16/3

b: B(x)=0

=>5x^2-125=0

=>x^2-25=0

=>x=5 hoặc x=-5

c: C(x)=0

=>2x^2-x-3=0

=>2x^2-3x+2x-3=0

=>(2x-3)(x+1)=0

=>x=3/2 hoặc x=-1

Đề bài sai rồi bạn