Answer:
[tex]\large\boxed{B.\ x=\dfrac{5+\sqrt{21}}{2},\ C.\ x=\dfrac{5-\sqrt{21}}{2}}[/tex]
Step-by-step explanation:
[tex]\text{Use the quadratic formula:}\\\\ax^2+bx+c=0\\\\x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}\\\\================================\\\\\text{We have}:\\\\x^2+1=5x\qquad\text{subtract}\ 5x\ \text{from both sides}\\\\x^2-5x+1=0\\\\a=1,\ b=-5,\ c=1\\\\b^2-4ac=(-5)^2-4(1)(1)=25-4=21\\\\x=\dfrac{-(-5)\pm\sqrt{21}}{2(1)}=\dfrac{5\pm\sqrt{21}}{2}[/tex]
