Tìm x biết (x+3)(x+3)=16

2 câu trả lời

`(x+3)(x+3)=16`

`<=>(x+3)^2=16`

`<=>(x+3)^2=4^2`

`<=>[(x+3=4),(x+3=-4):}`

`<=>[(x=4-3),(x=(-4)-3):}`

`<=>[(x=1),(x=-7):}`

Vậy `x=1;x=-7`

`(x+3)(x+3)= 16`

`=> (x+3)^2 = 16`

`=> (x+3)^2 = (+-4)^2`

`=>x+3=4` hoặc `x+3=-4`

`+)x+3=4`

`=>x=4-3`

`=>x=1`

`+)x+3=-4`

`=>x=-4-3`

`=>x=-7`

Vậy `x \in {1 ; -7}`