Toán Làm tính nhân: a) (x2 – 2x + 1)(x – 1) b) (x3 – 2×2 + x – 1)(5- x) 31/08/2021 By Quinn Làm tính nhân: a) (x2 – 2x + 1)(x – 1) b) (x3 – 2×2 + x – 1)(5- x)
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 ! Trả lời
$a) (x^2 – 2x + 1)( x – 1)$ $= x^2.(x – 1) + (–2x).(x – 1) + 1.(x – 1)$ $= x^2.x + x^2.(– 1) + (– 2x).x + (–2x).(–1) + 1.x + 1.(–1)$ $= x^3 – x^2 – 2x^2 + 2x + x – 1$ $= x^3 – (x^2 + 2x^2) + (2x + x) – 1$ $= x^3 – 3x^2 + 3x – 1$ $b) (x^3 – 2x^2 + x – 1)(x – 5)$ $= (x^3 – 2x^2 + x – 1).[–(5 – x)]$ $= – (x^3 – 2x^2 + x – 1).(5 – x)$ $= – (–x^4 + 7x^3 – 11x^2 + 6x – 5)$ $= x^4 – 7x^3 + 11x^2 – 6x + 5$ Trả lời
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 !
$a) (x^2 – 2x + 1)( x – 1)$
$= x^2.(x – 1) + (–2x).(x – 1) + 1.(x – 1)$
$= x^2.x + x^2.(– 1) + (– 2x).x + (–2x).(–1) + 1.x + 1.(–1)$
$= x^3 – x^2 – 2x^2 + 2x + x – 1$
$= x^3 – (x^2 + 2x^2) + (2x + x) – 1$
$= x^3 – 3x^2 + 3x – 1$
$b) (x^3 – 2x^2 + x – 1)(x – 5)$
$= (x^3 – 2x^2 + x – 1).[–(5 – x)]$
$= – (x^3 – 2x^2 + x – 1).(5 – x)$
$= – (–x^4 + 7x^3 – 11x^2 + 6x – 5)$
$= x^4 – 7x^3 + 11x^2 – 6x + 5$