5x(4x 2 −2x+1)−2x(10x 2 −5x+2)=−36 5�.4�2+5�.(−2�)+5�.1+(−2�).10�2+(−2�).(−5�)+(−2�).2=−365x.4x 2 +5x.(−2x)+5x.1+(−2x).10x 2 +(−2x).(−5x)+(−2x).2=−36 20�3+(−10�2)+5�+(−20�3)+10�2+(−4�)=−3620x 3 +(−10x 2 )+5x+(−20x 3 )+10x 2 +(−4x)=−36 (20�3−20�3)+(−10�2+10�2)+(5�−4�)=−36(20x 3 −20x 3 )+(−10x 2 +10x 2 )+(5x−4x)=−36 �=−36x=−36 Vậy �=−36x=−36.

a. x 4 − 5 x 3 + 4 x − 5 − x 4 + 3 x 2 + 2 x + 1 x 4 −5x 3 +4x−5−x 4 +3x 2 +2x+1 = − 5 x 3 + 3 x 2 + 6 x − 4 =−5x 3 +3x 2 +6x−4 b. R ( x ) = x 4 − 5 x 3 + 4 x − 5 − ( − x 4 + 3 x 2 + 2 x + 1 ) R(x)=x 4 −5x 3 +4x−5−(−x 4 +3x 2 +2x+1) = x 4 − 5 x 3 + 4 x − 5 + x 4 − 3 x 2 − 2 x − 1 =x 4 −5x 3 +4x−5+x 4 −3x 2 −2x−1 = 2 x 4 − 5 x 3 − 3 x 2 + 2 x − 6 =2x 4 −5x 3 −3x 2 +2x−6

−− 2�42x 4 −3�3−3x 3 −3�2−3x 2 +6�+6x −2−2 �2−2x 2 −2 2�42x 4 −4�2−4x 2 2�2−3�+12x 2 −3x+1 −− −3�3−3x 3 +�2+x 2 +6�+6x −2−2 −3�3−3x 3 +6�+6x −− �2x 2 −2−2 �2x 2 −2−2 00 Vậy ta có phép chia hết và thương là �=2�2−3�+1Q=2x 2 −3x+1.

a. Thể tích hình hộp chữ nhất là: x . ( x + 1 ) ( x − 1 ) = x . ( x 2 − 1 ) = x 3 − x x.(x+1)(x−1)=x.(x 2 −1)=x 3 −x

b. Thể tích của hình hộp chữ nhật tại x = 4 là: 4 3 − 4 = 60 4 3 −4=60

−− 2�42x 4 −3�3−3x 3 −3�2−3x 2 +6�+6x −2−2 �2−2x 2 −2 2�42x 4 −4�2−4x 2 2�2−3�+12x 2 −3x+1 −− −3�3−3x 3 +�2+x 2 +6�+6x −2−2 −3�3−3x 3 +6�+6x −− �2x 2 −2−2 �2x 2 −2−2 00 Vậy ta có phép chia hết và thương là �=2�2−3�+1Q=2x 2 −3x+1.

5x(4x2 – 2x + 1) – 2x(10x2 – 5x + 2) = −36. ⇔ 20x3 – 10x + 5x – 20x3 + 10x – 4x + 36 = 0 ⇔ x = −36. Vậy x = −36.

a. x 4 − 5 x 3 + 4 x − 5 − x 4 + 3 x 2 + 2 x + 1 x 4 −5x 3 +4x−5−x 4 +3x 2 +2x+1 = − 5 x 3 + 3 x 2 + 6 x − 4 =−5x 3 +3x 2 +6x−4

b. R ( x ) = x 4 − 5 x 3 + 4 x − 5 − ( − x 4 + 3 x 2 + 2 x + 1 ) R(x)=x 4 −5x 3 +4x−5−(−x 4 +3x 2 +2x+1) = x 4 − 5 x 3 + 4 x − 5 + x 4 − 3 x 2 − 2 x − 1 =x 4 −5x 3 +4x−5+x 4 −3x 2 −2x−1 = 2 x 4 − 5 x 3 − 3 x 2 + 2 x − 6 =2x 4 −5x 3 −3x 2 +2x−6

5x(4x2 – 2x + 1) – 2x(10x2 – 5x + 2) = −36. ⇔ 20x3 – 10x + 5x – 20x3 + 10x – 4x + 36 = 0 ⇔ x = −36. Vậy x = −36.