`(11)/(x^2)-(25)/(x+5)^2=1`
`⇔11(x+5)^2-25x^2=x^2(x+5)^2`
`⇔110x+275-14x^2=x^4+10x^3+25x^2`
`⇔x^4+10x^3+39x^2-110x-275=0`
`⇔(x-1-\sqrt(21))(x-1+\sqrt(21))(x^2.....)=0`
`⇔(x-1-\sqrt(21))(x-1+\sqrt(21))=0` vì `(x^2.....>0)`
`⇔`\(\left[ \begin{array}{l}x=1+\sqrt(21)\\x=1-\sqrt(21)\end{array} \right.\)