Answers

2014-10-05T18:38:44+08:00
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
x =  \frac{-b(+-) \sqrt{b^{2}-4ac } }{2a}
x =  \frac{-(-6)(+-) \sqrt{ (-6)^{2}-4(1)(-25) } }{2(1)}
x =  \frac{6 (+-) \sqrt{136} }{2}
x =  \frac{6(+-)2 \sqrt{34} }{2}
x_{1}  =  3 +\sqrt{34}
 x_{2} = 3 -  \sqrt{34}
or in decimal
 x_{1}  = 8.83
 x_{2} = -2.83
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