Question 445514
{{{ x^2-7x-8=0 }}}
Use the quadratic equation
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
{{{ a = 1 }}}
{{{ b = -7 }}}
{{{ c = -8 }}}
{{{x = (-(-7) +- sqrt( (-7)^2-4*1*(-8) ))/(2*1) }}} 
{{{x = ( 7 +- sqrt( 49 + 32)) / 2 }}} 
{{{x = ( 7 +- sqrt( 81)) / 2 }}} 
{{{x = ( 7 + 9 ) / 2 }}} 
{{{ x = 8 }}}
and
{{{x = ( 7 - 9 ) / 2 }}} 
{{{ x = -1 }}}
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check answers:
{{{ x = -1 }}}
{{{ x^2-7x-8=0 }}}
{{{ (-1)^2-7*(-1)-8=0 }}}
{{{ 1 + 7 - 8 = 0 }}}
{{{ 0 = 0 }}}
You can check other answer