i believe that there are 2 answers to that since it is quadratic not 4..
the highest order of exponent will determine the number of solution
so as to the expression x²-6x-9=16 you will have:
transposing 16 to the left
x²-6x-9-16=0
x²-6x-25=0
since this can't be factored by mere inspection, then you use quadratic formula
[tex]x = \frac{-b(+-) \sqrt{b^{2}-4ac } }{2a} [/tex]
[tex]x = \frac{-(-6)(+-) \sqrt{ (-6)^{2}-4(1)(-25) } }{2(1)} [/tex]
[tex]x = \frac{6 (+-) \sqrt{136} }{2} [/tex]
[tex]x = \frac{6(+-)2 \sqrt{34} }{2} [/tex]
[tex]x_{1} = 3 +\sqrt{34} [/tex]
[tex] x_{2} = 3 - \sqrt{34} [/tex]
or in decimal
[tex] x_{1} = 8.83[/tex]
[tex] x_{2} = -2.83[/tex]
