2 câu trả lời
Đáp án:
`2x^2+12x-630`
`= 2.(x^2 + 6x - 315)`
`= 2.(x^2+21x−15x−315) `
`= 2.[x.(x + 21) - 15.(x + 21)]`
`= 2.(x + 21).(x -15)`
$#dariana$
` 2x^2 + 12x - 630 `
` = 2x^2 + ( 42x - 30x ) - 630 `
` = 2x^2 + 42x - 30x - 630 `
` = ( 2x^2 + 42x ) - ( 30x + 630 ) `
` = ( 2x . x + 2x . 21 ) - ( 30 . x + 30 . 21 ) `
` = 2x ( x + 21 ) - 30 . ( x + 21 ) `
` = ( 2x - 30 ) . ( x + 21 ) `
` = 2 ( x - 15 ) ( x + 21 ) `
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