(x+1)(x-5)+3=0 . Tìm x Question (x+1)(x-5)+3=0 . Tìm x in progress 0 Môn Toán Mít Mít 4 years 2020-10-14T19:51:42+00:00 2020-10-14T19:51:42+00:00 2 Answers 107 views 0
Answers ( )
`(x + 1)(x – 5) + 3 = 0`
`=> (t + 3)(t – 3) + 3 = 0`
`=> t^2 – 9 + 3 = 0` (ă đ ă ̉ ư )
`=> t^2 – 6 = 0`
`=> (x – 2)^2 – 6 = 0`
`=> (x – 2)^2 = 6`
`=> x = ± √6 + 2`
Đáp án:
Ta có :
`(x + 1)(x – 5) + 3 = 0`
Đặt `t = x – 2`
`=> (t + 3)(t – 3) + 3 = 0`
`=> t^2 – 9 + 3 = 0`
`=> t^2 – 6 = 0`
`=> (x – 2)^2 – 6 = 0`
`=> (x – 2)^2 = 6`
`=> x = ± √6 + 2`
Đề khác :
`(x – 1)(x – 5) + 3 = 0`
Đặt `t = x – 3`
`=> (t + 2)(t – 2) + 3 = 0`
`=> t^2 – 4 + 3 = 0`
`=> t^2 – 1 = 0`
`=> (t – 1)(t + 1) = 0`
`=> (x – 3 – 1)(x – 3 + 1) = 0`
`= > (x – 4)(x – 2) = 0`
=>
=>
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