Toán Lớp 8: Phân tích đa thức thành nhân tử : `a)` `10x-5xy` `b)` `9x(x-y)-18x+18y` `c)` `x^2-7x+6` `d)` `y^2-4x^2+4x-1`

Question

Toán Lớp 8:  Phân tích đa thức thành nhân tử : a) 10x-5xy b) 9x(x-y)-18x+18y c) x^2-7x+6 d) y^2-4x^2+4x-1

danvanthu · Answer

a)  $10x$ $-$ $5xy$   $=$ $5x(2-y)$    b)  $9x(x-y)$ $-$ $18x$ $+$ $18y$   $=$ $9x(x-y)$ $-$ $18(x-y)$   $=$ $9(x-y)(x-2)$    c)  $x^2$ $-$ $7x$ $+$ $6$   $=$ $x^2$ $-$ $6x$ $-$ $x$ $+$ $6$   $=$ $x(x-6)$ $-$ $(x-6)$   $=$ $(x-6)(x-1)$    d)  $y^2$ $-$ $4x^2$ $+$ $x$ $-$ $1$   $=$ $y^2$ $-$ $(4x^2$ $-$ $x$ $+$ $1)$   $=$ $y^2$ $-$ $(2x-1)^2$   $=$ $[y-(2x-1)]$$[y+(2x-1)]$   $=$ $(y-2x+1)$$(y+2x-1)$   $Ch&uacute;c$ $bạn$ $học$ $tốt!$

tuenhioanh · Answer

Giải đáp:     a, 10x - 5xy   = 5x.(2 - y)   ---------   b, 9x.(x - y) - 18x + 18y   =  9x.(x - y) - 18.(x - y)   = (9x - 18).(x - y)   = 9.(x - 2).(x- y)   ----------   c, x^2 - 7x + 6   = x - 1 - 6x + 6   = (x - 1) - 6.(x - 1)   = (x - 1).(x - 6)   ------------   d, y^2 - 4x^2 + 4x - 1   = y^2 - (4x^2 - 4x + 1)   = y^2 - [(2x)^2 -2. 2x. 1 + 1^2]   = y^2 - (2x - 1)^2   = [y - (2x - 1)].[y + (2x - 1)]   = (y - 2x + 1).(y + 2x - 1)   #dariana