Answer:
A
[tex]\frac{3+5i\sqrt{3} }{2}[/tex] or [tex]\frac{3-5i\sqrt{3} }{2}[/tex] (i cant do the 'plus or minus' sign on my laptop, but the answer is A )
Step-by-step explanation:
f(x)=x²-3x+21
(let f(x)=0)
x²-3x+21=0
Use the quadratic formula
[tex]\frac{-b + \sqrt{b^{2}-4ac } }{2a}[/tex] or [tex]\frac{-b - \sqrt{b^{2}-4ac } }{2a}[/tex]
[tex]\frac{-(-3) + \sqrt{(-3)^{2}-4(1)(21) } }{2(1)}[/tex] or [tex]\frac{-(-3) - \sqrt{(-3)^{2}-4(1)(21) } }{2(1)}[/tex]
[tex]\frac{3+\sqrt{-75} }{2}[/tex] or [tex]\frac{3-\sqrt{-75} }{2}[/tex]
[tex]\frac{3+5i\sqrt{3} }{2}[/tex] or [tex]\frac{3-5i\sqrt{3} }{2}[/tex]
