Hướng dẫn trả lời:
`x^2-25-(x+5)=0.`
`⇒(x^2-5^2)-1.(x+5)=0.`
`⇒(x-5).(x+5)-1.(x+5)=0.`
`⇒(x+5).[(x-5)-1]=0.`
`⇒(x+5).(x-5-1)=0.`
`⇒(x+5).(x-6)=0.`
$\text{⇒\(\left[ \begin{array}{l}x+5=0.\\x-6=0.\end{array} \right.\)}$
$\text{⇒\(\left[ \begin{array}{l}x=-5.\\x=6.\end{array} \right.\)}$
$\text{Vậy x = -5 hoặc x = 6.}$