Question

Tìm đa thức A biết: \(A-\left(3xy-4y^2\right)=x^2-7xy+8y^2\)

Answer 1

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

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

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

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

\(A=x^2-4xy+4y^2\)

\(A=\left(x-2y\right)^2\)

Answer 2

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

=>A=\(x^2-4xy+4y^2\)

=>A=\(\left(x-2y\right)^2\)

Vậy A=\(\left(x-2y\right)^2\)