Question

cho x-y=7.Tính giá trị biểu thức:

                    A=x(x+2)+y(y-2)-2xy+27.

Answer 1

\(A=x^2+2x+y^x-2y-2xy+27\)

\(A=\left(x^2-2xy+y^2\right)+2\left(x-y\right)+27\)

\(A=\left(x-y\right)^2+2.7+27\)

\(A=7^2+41=49+41=90\)

Answer 2

 

\(A=x^2+2x+y^2-2y-2xy+27\)

\(A=\left(x^2-2xy+y^2\right)+2\left(x-y\right)+27\)

\(A=\left(x-y\right)^2-2\left(x-y\right)+27\)

\(A=49-14+27=90\)

Answer 3

ớ cô lm j cho bài này