bài 1: a)x ∧ 4-16 ² =0 b)x ∧8+36x ∧4=0 d)5(x-2)-x ²+4=0 c)(x-5) ³-x+5=0

`a,` `x^4-16^2=0`

`⇒x^4=16^2`

`⇒x^4=(±4)^4`

`⇒x=±4`

`b,` `x^8+36x^4=0`

`⇒x^4(x^4+36)=0`

$⇒\left[ \begin{array}{l}x^4=0\\x^4+36=0\end{array} \right.⇒\left[ \begin{array}{l}x=0\\x^4=-36\text{(vô lý)}\end{array} \right.$

`c,` `(x-5)^3-x+5=0`

`⇒(x-5)^3-(x-5)=0`

`⇒(x-5)[(x-5)^2-1]=0`

$⇒\left[ \begin{array}{l}x-5=0\\(x-5)^2-1=0\end{array} \right.⇒\left[ \begin{array}{l}x=5\\\left[ \begin{array}{l}x-5=1\\x-5=-1\end{array} \right.⇒\left[ \begin{array}{l}x=6\\x=-4\end{array} \right.\end{array} \right.$

`d,` `5(x-2)-x^2+4=0`

`5(x-2)-(x+2)(x-2)=0`

`(x-2)(5-x-2)=0`

$⇒\left[ \begin{array}{l}x-2=0\\5-x-2\end{array} \right.⇒\left[ \begin{array}{l}x=2\\x=3\end{array} \right.$