Question

x2-81=0 formula general

Answer 1

Por formula cuadratica: 

$\frac{-b + \sqrt{ b^{2}-4ac } }{2a} = \frac{ \sqrt{(0)^{2}-(1)(-81) } }{2(1)} = \frac{ \sqrt{324} }{2} = \frac{18}{2} =9$

$\frac{-b - \sqrt{ b^{2}-4ac } }{2a} = \frac{ \sqrt{(0)^{2}-(1)(-81) } }{2(1)} = -\frac{ \sqrt{324} }{2} = \frac{-18}{2} =-9$