rút gon biểu thức sau: P= 2.(x+y).(x-y)-(x-y)^2+(x+y)^2-4y^2 giúp tui vs ạ 01/07/2021 Bởi Arya rút gon biểu thức sau: P= 2.(x+y).(x-y)-(x-y)^2+(x+y)^2-4y^2 giúp tui vs ạ
$P=2(x+y)(x-y)-(x-y)^2+(x+y)^2-4y^2$ $=2(x^2-y^2)-(x^2-2xy+y^2)+(x^2+2xy+y^2)-4y^2$ $=2x^2-2y^2-x^2+2xy-y^2+x^2+2xy+y^2-4y^2$ $=(2x^2-x^2+x^2)+(-2y^2-y^2+y^2-4y^2)+(2xy+2xy)$ $=2x^2-6y^2+4xy$ Vậy $P=2x^2+4xy-6y^2$ Bình luận
`P = 2. (x + y). (x – y) – (x – y)^2 + (x + y)^2 – 4y^2` `= (2x + 2y). (x – y) – (x^2 – 2xy + y^2) + (x^2 + 2xy + y^2) – 4y^2` `= (2x^2 + 2xy – 2xy – 2y^2) – x^2 + 2xy – y^2 + x^2 + 2xy + y^2 – 4y^2` `= 2x^2 – 2y^2 – x^2 + 2xy – y^2 + x^2 + 2xy + y^2 – 4y^2` `= (2x^2 – x^2 + x^2) – (2y^2 + y^2 – y^2 + 4y^2) + (2xy + 2xy)` `= 2x^2 – 6y^2 + 4xy` Bình luận
$P=2(x+y)(x-y)-(x-y)^2+(x+y)^2-4y^2$
$=2(x^2-y^2)-(x^2-2xy+y^2)+(x^2+2xy+y^2)-4y^2$
$=2x^2-2y^2-x^2+2xy-y^2+x^2+2xy+y^2-4y^2$
$=(2x^2-x^2+x^2)+(-2y^2-y^2+y^2-4y^2)+(2xy+2xy)$
$=2x^2-6y^2+4xy$
Vậy $P=2x^2+4xy-6y^2$
`P = 2. (x + y). (x – y) – (x – y)^2 + (x + y)^2 – 4y^2`
`= (2x + 2y). (x – y) – (x^2 – 2xy + y^2) + (x^2 + 2xy + y^2) – 4y^2`
`= (2x^2 + 2xy – 2xy – 2y^2) – x^2 + 2xy – y^2 + x^2 + 2xy + y^2 – 4y^2`
`= 2x^2 – 2y^2 – x^2 + 2xy – y^2 + x^2 + 2xy + y^2 – 4y^2`
`= (2x^2 – x^2 + x^2) – (2y^2 + y^2 – y^2 + 4y^2) + (2xy + 2xy)`
`= 2x^2 – 6y^2 + 4xy`