Question

BT8: Cho hai đa thức\(M=\left[x+\left(y-z\right)-2x\right]+y+z-\left(2-x-y\right)\)và\(N=x-\left[x-\left(y-z\right)-x\right]\)

Tính M+N và M-N

Answer 1

\(M=\left[x+\left(y-z\right)-2x\right]+y+z-\left(2-x-y\right)\)

\(=-x+y-z+y+z-2+x+y\)

\(=3y-2\)

\(N=x-\left[x-\left(y-z\right)-x\right]\)

\(=x-\left(-y+z\right)\)

\(=x+y-z\)

\(M+N=3y-2+x+y-z=x+4y-z-2\)

\(M-N=\left(3y-2\right)-\left(x+y-z\right)\)

\(=3y-2-x-y+z\)

\(=-x+2y+z-2\)

Answer 2

\(M=\left[x+\left(y-z\right)-2x\right]+y+z-\left(2-x-y\right)\\ M=x+y-z-2x+y+z-2+x+y\\ M=3y-2\)

 

\(N=x-\left[x-\left(y-z\right)-x\right]\\ N=x-\left(x-y+z-x\right)\\ N=x-x+y-z+x\\ N=x+y-z\)

 

\(M+N=3y-2+x+y-z\\ M+N=x+4y-z-2\)

 

\(M-N=3y-2-\left(x+y-z\right)\\ M-N=3y-2-x-y+z\\ M-N=-x+2y+z-2\)