a , 7 . ( x -2 ) – 5 ( x – 4) = 28 b , ( x – 3 )² – 48 = -12 c , -7 – 2x = -37 – ( -26 ) 08/11/2021 Bởi Autumn a , 7 . ( x -2 ) – 5 ( x – 4) = 28 b , ( x – 3 )² – 48 = -12 c , -7 – 2x = -37 – ( -26 )
`\text{a)}` `7(x – 2) – 5(x – 4) = 28` `7(x – 2) = 28 + 5(x – 4)` `7x – 14 = 28 + 5x – 20` `7x – 5x = 28 – 20 + 14` `2x = 22` `x = 11` `\text{b)}` `(x – 3)^2 – 48 = -12` `(x – 3)^2 = -12 + 48` `(x – 3)^2 = 36` `(x – 3)^2 = 6^2` `⇒ x -3 = 6 → x = 9` `\text{hoặc}` `x -3 = -6 ⇒ x = -3` `\text{c)}` `-7 -2x = -37 – (-26)` `-7 – 2x = -11` ` 2x = -7 +11` `2x = 4` `x = 2` Bình luận
`\text{a)}`
`7(x – 2) – 5(x – 4) = 28`
`7(x – 2) = 28 + 5(x – 4)`
`7x – 14 = 28 + 5x – 20`
`7x – 5x = 28 – 20 + 14`
`2x = 22`
`x = 11`
`\text{b)}`
`(x – 3)^2 – 48 = -12`
`(x – 3)^2 = -12 + 48`
`(x – 3)^2 = 36`
`(x – 3)^2 = 6^2`
`⇒ x -3 = 6 → x = 9` `\text{hoặc}` `x -3 = -6 ⇒ x = -3`
`\text{c)}`
`-7 -2x = -37 – (-26)`
`-7 – 2x = -11`
` 2x = -7 +11`
`2x = 4`
`x = 2`
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