Question 63113
can you help me solve by using the quadratic formula of x^2-4x-5=0?
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Here it is step by step:
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In the form ax^2 + bx + c = 0; your problem: a=1; b=-4; -5
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{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
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{{{x = (-(-4) +- sqrt( (-4)^2-4*1*-5 ))/(2*1) }}}
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{{{x = (+4 +- sqrt( 16 - (-20) ))/(2) }}}
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 {{{x = (4 +- sqrt( 16 + 20 ))/(2) }}}
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{{{x = (4 +- sqrt( 36 ))/(2) }}}
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{{{x = (4 +- 6 )/2 }}}
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Solution using +6:
{{{x = (4 + 6 )/2 }}}
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{{{x = 10/2 }}}
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x = +5
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Solution using -6:
{{{x = (4 - 6 )/2 }}}
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{{{ x = -2/2 }}}
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x = -1
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Learn this and you can do them all the same way!