Cách làm cho bạn:
- \(M+N=3xyz-3x^2+5xy-1+5x^2+xyz-5xy+3-y\)
\(=(-3x^2+5x^2)+(3xyz+xyz)+(5xy-5xy)+(-1+3)-y\)
\(=2x^2+4xyz+0+2-y\)
\(=2x^2+4xyz-y+2\)
- \(M-N=3xyz-3x^2+5xy-1-(5x^2+xyz-5xy+3-y)\)
\(=3xyz-3x^2+5xy-1-5x^2-xyz+5xy-3+y\)
\(=(3xyz-xyz)+(-3x^2-5x^2)+(5xy+5xy)+(-1-3)+y\)
\(=2xyz-8x^2+10xy+y-4\)
- \(N-M=5x^2+xyz-5xy+3-y-(3xyz-3x^2+5xy-1)\)
\(=5x^2+xyz-5xy+3-y-3xyz+3x^2-5xy+1\)
\(=(5x^2+3x^2)+(xyz-3xyz)+(-5xy-5xy)+(3+1)-y\)
\(=8x^2-2xyz-10xy-y+4\)
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