Toán Lớp 8: Bài 1: Tính
a) (x^2 – 2xy + y^2 )(x – 2y)
b) (x + y + z)(x – y + z)
c) (2x^2 – 3x + 5)(x^2 – 8x + 2)
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Toán Lớp 8: Bài 1: Tính
a) (x^2 – 2xy + y^2 )(x – 2y)
b) (x + y + z)(x – y + z)
c) (2x^2 – 3x + 5)(x^2 – 8x + 2)
Comments ( 2 )
$=x^2.(x-2y)-2xy.(x-2y)+y^2.(x-2y)$
$=x^3-2x^2y-2x^2y+4xy^2+xy^2-2y^3$
$=x^3-4x^2y+5xy^2-2y^3$
$b)(x+y+z).(x-y+z)$
$=x.(x-y+z)+y.(x-y+z)+z.(x-y+z)$
$=x^2-xy+xz+xy-y^2+yz+xz-yz+z^2$
$=x^2+2xz-y^2+z^2$
$c)(2x^2-3x+5).(x^2-8x+2)$
$=2x^2.(x^2-8x+2)-3x.(x^2-8x+2)+5.(x^2-8x+2)$
$=2x^4-16x^3+4x^2-3x^3+24x^2-6x+5x^2-40x+10$
$=2x^4-19x^3+33x^2-46x+10$
@Nobitao@