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, \(A=3xy-4y^2-x^2+7xy-8y^2=-x^2+10xy-12y^2\)

a/

 \(M+5x^2-2xy-6x^2-9xy+y^2=0\)

\(M-x^2-11xy+y^2=0\)

\(M-x^2+y^2-11xy=0\)

\(M=x^2-y^2+11xy\)

Vậy:..

Câu b tương tự

M + (5x² - 2xy) = 6x² + 9xy - y^{2   ta có} M = ( 6x² + 9xy - y^{2) -(}5x² - 2xy)= x2 +11xy -y2

\(M=6x^2+9xy-y^2-5x^2+2xy\)

\(M=x^2+11xy-y^2\)

\(N=3xy-4y^2-x^2+7xy-8y^2\)

\(N=-x^2+10xy-12y^2\)

a.    \(M+\left(5x^2-2xy\right)=6x^2+9xy-y^2\)

\(\Rightarrow M=6x^2+9xy-y^2-5x^2+2xy\)

b.     \(\left(3xy-4y^2\right)-N=x^2-7xy+8y^2\)

\(\Rightarrow N=3xy-4y^2-x^2+7xy-8y^2\)

a: \(M=6x^2+9xy-y^2-5x^2+2xy=x^2+11xy-y^2\)

b: \(N=3xy-4y^2-x^2+7xy-8y^2=-x^2+10xy-12y^2\)

a) M + (5x² - 2xy) = 6x² + 9xy - y²

=> M = (6x² + 9xy - y²) - (5x² - 2xy)

=> M = 6x² + 9xy - y² - 5x² + 2xy = (6x² - 5x²) + (9xy + 2xy) - y² = x² + 11xy - y²

b) Sửa đề lại đi nhé

c) (25x²y - 13x²y + y³) - M = 11x²y - 2y²

=> M = (25x²y - 13x²y + y³) - (11x²y - 2y²)

=> M = 25x²y - 13x²y + y³ - 11x²y + 2y²

=> M = x²y + y³ + 2y²

d) M = 0 - (12x⁴ - 15x²y + 2xy² + 7) = -12x⁴ + 15x²y - 2xy² - 7

a) Ta có : M = 6x² + 9xy - y² - (5x² - 2xy)

                    =  6x² + 9xy - y² - 5x² + 2xy

                    = x² + 11xy - y²

b) Ta có M = x² - 7xy + 8y² - (3xy - 24y²)

                 = x² - 7xy + 8y² - 3xy + 24y²

                  = x² - 10xy + 32y²

c) Ta có M = 25x².y- 13x²y + y³ - (11x²y - 2y²)

                  = 25x².y- 13x²y + y³ - 11x²y + 2y²

                 = x²y + y³ + 2y²

d) Ta có M = -(12x⁴ - 15x²y + 2xy² + 7)

                 =  -12x⁴ + 15x²y - 2xy² - 7

a) Có:

\(M+\left(5x^2-2xy\right)=6x^2+9xy-y^2\)

\(\Rightarrow M=6x^2+9xy-y^2-\left(5x^2-2xy\right)\)

\(M=6x^2+9xy-y^2-5x^2+2xy\)

\(M=\left(6x^2-5x^2\right)+\left(9xy+2xy\right)-y^2\)

\(\Rightarrow M=x^2+11xy-y^2\)

b) Có:

\(\left(3xy-4y^2\right)-N=x^2-7xy+8y^2\)

\(\Rightarrow N=3xy-4y^2-\left(x^2-7xy+8y^2\right)\)

\(N=3xy-4y^2-x^2+7xy-8y^2\)

\(N=\left(3xy+7xy\right)+\left(-4y^2-8y^2\right)-x^2\)

\(\Rightarrow N=10xy+\left(-12y^2\right)-x^2\)

Hay \(N=10xy-12y^2-x^2\)

Chúc bạn học tốt!

a, (6x²+9xy-y²) - ( 5x²-2xy)=M

=> M= (6x²+9xy-y²) - ( 5x²-2xy)

=> M= 6x²+9xy-y² - 5x²+2xy

=> M=(6x²- 5x²)+(9xy+2xy)-y²

=>M= 1x² + 11xy - y²

Vậy M= 1x² + 11xy - y²

b, N= (3xy-4y²) - (x²-7xy+8y²)

=> N= 3xy-4y² - x²+7xy-8y²

=> N= (3xy+7xy)-(4y²+8y²)-x²

=> N= 10xy - 12y² -x²

Vậy N= 10xy - 12y² -x²

Chúc bạn học tốt nha!!!

a, M+(5x²-2xy)=6x²+9xy-y²

\(\Rightarrow\)M= (6x²+9xy-y²)-(5x²-2xy)

= 6x²+9xy-y²-5x²+2xy

= (6x²-5x²)+(9xy+2xy)-y²

= x²+11xy-y²

Vậy đa thức M= x²+11xy-y²

b, (3xy-4y²)-N=x²-7xy+8y²

\(\Rightarrow\)N= (3xy-4y²)-(x²-7xy+8y²)

= 3xy-4y²-x²+7xy-8y²

= (3xy+7xy)+(-4y²-8y²)-x²

= 10xy-12y²-x²

Vậy đa thức N=10xy-12y²-x²

a) M = (6x²+9xy-y²) - (5x²-2xy)

M=(6x²+5x²⁾+(9xy-2xy)-y²

M=11x²+7xy-y2

b)N = (3xy-4y²) - (x²-7xy+8y²)

N= 3xy-4y²-x²+7xy-8y²

N=(3xy+7xy)-x²+(-4y²-8y²)

N=10xy-x²-12y²

phép trừ của N đổi dấu vế thứ 2