Câu hỏi của Takanashi Hikari

Question

Phân tích:

a) $3x^2+9x-30$

b) $3x^2-5x-2$

c) $x^2-7xy+10y^2$

d) $x^3-7x-6$

e) $x^2-2x-y^2+4y-3$

Giúp mình giải bài này nhé, thanks!!!

Nguyễn Việt Lâm · Accepted Answer

a/ $=3x^2+15x-6x-30$

$=3x\left(x+5\right)-6\left(x+5\right)$

$=3\left(x-2\right)\left(x+5\right)$

b/ $=3x^2-6x+x-2$

$=3x\left(x-2\right)+x-2$

$=\left(3x+1\right)\left(x-2\right)$

c/ $=x^2-2xy-5xy+10y^2$

$=x\left(x-2y\right)-5y\left(x-2y\right)$

$=\left(x-5y\right)\left(x-2y\right)$

d/ $=x^3+3x^2+2x-3x^2-9x-6$

$=x\left(x^2+3x+2\right)-3\left(x^2+3x+2\right)$

$=\left(x-3\right)\left(x^2+3x+2\right)=\left(x-3\right)\left(x+1\right)\left(x+2\right)$

e/ $=x^2-2x+1-\left(y^2-4y+4\right)$

$=\left(x-1\right)^2-\left(y-2\right)^2$

$=\left(x-y+1\right)\left(x+y-3\right)$Câu trả lời: a/ $=3x^2+15x-6x-30$