Làm tính chia:
Bài 80. Làm tính chia:
a) \(\left( {6{x^3} – 7{x^2} – x + 2} \right):\left( {2x + 1} \right)\)
b) \(\left( {{x^4} – {x^3} + {x^2} + 3x} \right):\left( {{x^2} – 2x + 3} \right)\) ;
c) \(\left( {{x^2} – {y^2} + 6x + 9} \right):\left( {x + y + 3} \right)\) .
Hướng dẫn làm bài:
b) 
c) \(\left( {{x^2} – {y^2} + 6x + 9} \right):\left( {x + y + 3} \right)\)
=\(\left( {{x^2} + 6x + 9 – {y^2}} \right)\left( {x + y + 3} \right)\)
=\(\left[ {\left( {{x^2} + 2x.3 + {3^2}} \right) – {y^2}} \right]:\left( {x + y + 3} \right)\)
=\(\left[ {{{\left( {x + 3} \right)}^2} – {y^2}} \right]:\left( {x + y + 3} \right)\)
=\(\left( {x + 3 – y} \right)\left( {x + 3 + y} \right):\left( {x + y + 3} \right)\)
= \(x + 3 – y\)
= \(x – y + 3\)
