<PRE><B>Question 7165</B>
{{{ x^2-4x-9=0 }}}
The above equation is in the form of {{{AX^2 + BX + C = 0}}}

where A=1,B= -4 , c= -9

Roots of the quadratic equation is found by 
{{{x= -b +- sqrt(b^2 -4ac ) /2a }}}

Substututing the values of A,B, in the formula above

{{{x = 4 +- sqrt ((-4)^2 -  4 *1* -9)/2}}}
{{{ x= 4+- sqrt( 16 +36)/2}}}
{{{ x= 4+- sqrt(52)/2}}}
solving we get
x1=  5.6056
x2=  -1.6056</PRE>