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`

TRẢ LỜI

1. 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)$

   $Chúc$ $bạn$ $học$ $tốt!$

   Trả lời
2. 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

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