A) x (x-2)+x (x+1) B) 3x (x-y)+2 (y-x) C) 7 (x+1)-(x+1)×(x-2) D) 9x^2-(3x-2)^2 (^ mũ) Giúp với cần gấp 14/07/2021 Bởi Emery A) x (x-2)+x (x+1) B) 3x (x-y)+2 (y-x) C) 7 (x+1)-(x+1)×(x-2) D) 9x^2-(3x-2)^2 (^ mũ) Giúp với cần gấp
`a) = x^2-2x+x^2+x` `= 2x^2-x` `b) = 3x^2-3xy+2y-2x` `c) =7x+7-(x^2-2x+x-2)` `= 7x+7-x^2+x+2` `= -x^2+8x+9` `d) = 9x^2-(9x^2-12x+4)` `= 9x^2-9x^2+12x+4` `= 12x+4` Bình luận
Đáp án: A) `x (x-2)+x (x+1)` = `x.x – x.2 + x .x + x.1` = `x^2-2x+x^2+x` =` 2x^2 – x` B) `3x (x-y)+2 (y-x)` = ` 3x.x – 3x.y + 2.y -2.x` = ` 3x^2-3xy+2y-2x` C) `7 (x+1)-(x+1).(x-2)` = ` 7.x + 7.1 – (x+1). x + (x+1) .2` = `7x + 7 -x.x – 1.x + x.2 +1.2` = ` 7x +7 -x^2-x +2x +2` = ` -x^2 +8x +2` D) `9x^2-(3x-2)^2` = `9x^2-((3x^2)-2.2.3x+2^2) ` = ` 9x^2 -9x^2 + 12x + 4` = ` 12x +4` Bình luận
`a) = x^2-2x+x^2+x`
`= 2x^2-x`
`b) = 3x^2-3xy+2y-2x`
`c) =7x+7-(x^2-2x+x-2)`
`= 7x+7-x^2+x+2`
`= -x^2+8x+9`
`d) = 9x^2-(9x^2-12x+4)`
`= 9x^2-9x^2+12x+4`
`= 12x+4`
Đáp án:
A) `x (x-2)+x (x+1)` = `x.x – x.2 + x .x + x.1`
= `x^2-2x+x^2+x`
=` 2x^2 – x`
B) `3x (x-y)+2 (y-x)` = ` 3x.x – 3x.y + 2.y -2.x`
= ` 3x^2-3xy+2y-2x`
C) `7 (x+1)-(x+1).(x-2)` = ` 7.x + 7.1 – (x+1). x + (x+1) .2`
= `7x + 7 -x.x – 1.x + x.2 +1.2`
= ` 7x +7 -x^2-x +2x +2`
= ` -x^2 +8x +2`
D) `9x^2-(3x-2)^2` = `9x^2-((3x^2)-2.2.3x+2^2) `
= ` 9x^2 -9x^2 + 12x + 4`
= ` 12x +4`