Question 235865
{{{x^2+14x-4=0}}} 
Is the answer x=0.28,14.28 
I don't think that's right

<pre><font size = 4 color = "indigo"><b>

Checkley said yes, so let's find out for sure:

{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 

with {{{a=1}}}, {{{b=14}}}, {{{c=-4}}}

{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 

{{{x = (-(14) +- sqrt( (14)^2-4*(1)*(-4) ))/(2*(1)) }}} 

{{{x = (-14 +- sqrt(196+16 ))/2 }}}

{{{x = (-14 +- sqrt(212 ))/2 }}}

{{{x = (-14 +- sqrt(4*53 ))/2 }}} 

{{{x = (-14 +- 2*sqrt(53 ))/2 }}}

{{{x = (-14)/2 +- (2*sqrt(53 ))/2 }}}

{{{x = -7 +- sqrt(53 ) }}}

Using the +,

{{{x = -7 + sqrt(53 ) }}}

Using a calculator:

{{{x = -7 + 7.280109889 = 0.280109889}}}

That rounds off to 0.28, so you're right on that one.


Using the -,

{{{x = -7 - sqrt(53 ) }}}

Using a calculator:

{{{x = -7 - 7.280109889 = -14.280109889}}}

That rounds off to -14.28.  Uh oh! You missed the
sign on that one. Checkley didn't notice.
But you were half right!

Edwin</pre>