a) (x^2 – 2x + 1)(x – 1)
= x2.(x – 1) - 2x.(x – 1) + 1.(x – 1)
= x2.x + x2.(– 1) - 2x.x - 2x.(–1) + 1.x + 1.(–1)
= x3 – x2 – 2x2 + 2x + x – 1
= x3 – (x2 + 2x2) + (2x + x) – 1
= x3 – 3x2 + 3x – 1
b) (x^3 – 2x^2 + x – 1)(5- x)
= (x3 – 2x2 + x – 1).5 + (x3 – 2x2 + x – 1).(–x)
= x3.5 - 2x2.5 + x.5 - 1.5 + x3.(–x) - 2x2.(–x) + x.(–x) - 1.(–x)
= 5x3 – 10x2 + 5x – 5 – x4 + 2x3 – x2 + x
= –x4 + (5x3 + 2x3) – (10x2 + x2) + (5x + x) – 5
= –x4 + 7x3 – 11x2 + 6x – 5
xin hay nhất ạ !
