[tex]( {x}^{2} + 1 {)}^{2} - 10( {x}^{2} + 1) + 25 = 0 \\ ( {x}^{2} + 1) = j \\ {j}^{2} - 10j + 25 = 0 \\ D = ( - 10 {)}^{2} - 4 \times 1 \times 25 = 100 - 100 = 0 \\ j = \frac{10}{2 \times 1} = 5 \\ ( {x}^{2} + 1) = 5 \\ {x}^{2} = 4 \\ x = 2 \: \: \: \: \: \: x = - 2 [/tex]