Toán a)A=2x^2-5x-2x(x+1) b)B=(x+2y)(x-2y)-4y(x-y) 03/08/2021 By Kylie a)A=2x^2-5x-2x(x+1) b)B=(x+2y)(x-2y)-4y(x-y)
Đáp án: Giải thích các bước giải: a) `A=2x^2-5x-2x(x+1)` `A=2x^2-5x-2x^2-2x` `A=-7x` b) `B=(x+2y)(x-2y)-4y(x-y)` `B=x^2-4y^2-4xy+4y^2` `B=x^2-4xy=x(x-4y)` Trả lời
a) $2x^2-5x-2x(x+1)$ $=2x^2-5x-2x^2-2x$ $=(2x^2-2x^2)+(-5x-2x)$ $=0-7x=-7x$ b) $(x+2y)(x-2y)-4y(x-y)$ $=x(x-2y)+2y(x-2y)-4xy+4y^2$ $=x^2-2xy+2xy-4y^2-4xy+4y^2$ $=x^2+(-2xy+2xy-4xy)+(-4y^2+4y^2)$ $=x^2-4xy$ Trả lời
Đáp án:
Giải thích các bước giải:
a) `A=2x^2-5x-2x(x+1)`
`A=2x^2-5x-2x^2-2x`
`A=-7x`
b) `B=(x+2y)(x-2y)-4y(x-y)`
`B=x^2-4y^2-4xy+4y^2`
`B=x^2-4xy=x(x-4y)`
a) $2x^2-5x-2x(x+1)$
$=2x^2-5x-2x^2-2x$
$=(2x^2-2x^2)+(-5x-2x)$
$=0-7x=-7x$
b) $(x+2y)(x-2y)-4y(x-y)$
$=x(x-2y)+2y(x-2y)-4xy+4y^2$
$=x^2-2xy+2xy-4y^2-4xy+4y^2$
$=x^2+(-2xy+2xy-4xy)+(-4y^2+4y^2)$
$=x^2-4xy$