Y = x^4-5x^2+4 найти нули функции

[latex] x^{4}-5 x^{2}+4=0 \\ x^{2} =t \\ t^{2} -5t+4=0 \\ D= b^{2}-4ac= 25- 4*1*4=9 \\ [latex] \\ x_{1}= \frac{-b+ \sqrt{D} }{2a}= \frac{5+3}{2*1}=4 \\ x_{2}= \frac{-b- \sqrt{D} }{2a}= \frac{5-3}{2*1}=1 \\ 1) x^{2} =t \\ x^{2} = 4 \\ x=+и-2 \\ 2) x^{2} =1 \\ x= + и -1[/latex]