Tìm x: (x+5)(x-1)= (x+7)^2 Question Tìm x: (x+5)(x-1)= (x+7)^2 in progress 0 Môn Toán Orla Orla 4 years 2020-10-31T12:44:20+00:00 2020-10-31T12:44:20+00:00 2 Answers 65 views 0
Answers ( )
`=> x^2+4x-5=x^2+14x+49`
`=> 10x +49+5=0`
`=> 10x = -54`
`=> x = -5,4`
Đáp án:
`x=-27/5`
Giải thích các bước giải:
`(x+5)(x-1)=(x+7)^2`
`⇔x^2-x+5x-5=x^2+2.x.7+7^2`
`⇔x^2+4x-5=x^2+14x+49`
`⇔x^2+14x+49-x^2-4x+5=0`
`⇔10x+54=0`
`⇔10x=-54`
`⇔x=-54/10=-27/5`
vậy `x=-27/5`