Nội dung bài giảng
Thu gọn các đa thức sau:
a) \({\rm{}}2{{\rm{x}}^2}yz + 4{\rm{x}}{y^2}z - 5{{\rm{x}}^2}yz + x{y^2}z - xyz\)
b) \({x^3} - 5{\rm{x}}y + 3{{\rm{x}}^3} + xy - {x^2} + {1 \over 2}xy - {x^2}\)
Giải
\(\eqalign{
& {\rm{a}})2{{\rm{x}}^2}yz + 4{\rm{x}}{y^2}z - 5{{\rm{x}}^2}yz + x{y^2}z - xyz \cr
& = (2 - 5){x^2}yz + (4 + 1)x{y^2}z - xyz \cr
& = - 3{{\rm{x}}^2}yz + 5{\rm{x}}{y^2}z - xyz \cr} \)
\(\eqalign{
& b){x^3} - 5{\rm{x}}y + 3{{\rm{x}}^3} + xy - {x^2} + {1 \over 2}xy - {x^2} \cr
& = (1 + 3){x^3} - \left( {5 - 1 - {1 \over 2}} \right)xy - (1 + 1){x^2} \cr
& = 4{{\rm{x}}^3} - {7 \over 2}xy - 2{{\rm{x}}^2} \cr} \)