Question

Tìm X

A,(x-1)^2=6

B,3x^2-6=0

C,(x-2) (2x+1)=0

D,x^2-4x+4=0

E,x^2-8x+7=0

F,x^4-256=0

Answer 1

`a)(x-1)^2=6`

\(\Leftrightarrow\left[{}\begin{matrix}x-1=\sqrt{6}\\x-1=-\sqrt{6}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1+\sqrt{6}\\x=1-\sqrt{6}\end{matrix}\right.\)

`b)3x^2-6=0`

`<=>3x^2=6`

`<=>x^2=2`

\(\Leftrightarrow x=\pm\sqrt{2}\)

`c)(x-2)(2x+1)=0`

`TH1:x-2=0`

`<=>x=2`

`TH2:2x+1=0`

`<=>2x=-1`

`<=>x=-1/2`

`d)x^2-4x+4=0`

`<=>(x-2)^2=0`

`<=>x=2`

`e)x^2-8x+7=0`

`<=>(x^2-x)+(-7x+7)=0`

`<=>x(x-1)-7(x-1)=0`

`<=>(x-1)(x-7)=0`

TH1: `x-1=0`

`<=>x=1`

TH2: `x-7=0`

`<=>x=7`

`f)x^4-256=0`

`<=>(x^2-16)(x^2+16)=0`

`<=>(x-4)(x+4)(x^2+16)=0`

Mà: `x^2+16>=16>0`

`=>x-4=0` hoặc `x+4=0`

`<=>x=+-4`