Question 389612
<pre>

Use the quadratic formula to solve the equations:
    {{{0 = x^2 + x - 20}}}

Write as

{{{x^2 + x - 20=0}}}

and then as

{{{1*x^2 + 1*x + (-20)=0}}}

and compare to this form which you must memorize:

{{{A*x^2 + B*x + C = 0}}}

We see that A=1, B=1, C=-20.  and we substitute into
this formula which you must also memorize:
   
{{{x = (-B +- sqrt( B^2-4*A*C ))/(2*A) }}} 

{{{x = (-(1) +- sqrt( (1)^2-4*(1)*(-20) ))/(2*(1)) }}}

{{{x = (-1 +- sqrt( 1+80))/2 }}}

{{{x = (-1 +- sqrt(81))/2 }}}

{{{x = (-1 +- 9)/2 }}}

Use the + for the first solution:

{{{x = (-1 + 9)/2 }}}

{{{x = 8/2 }}}

{{{x = 4}}}  That's the first solution.

Use the - for the second solution:

{{{x = (-1 - 9)/2 }}}

{{{x = (-10)/2 }}}

{{{x = -5}}}  That's the second solution.

There are two solutions x = 4 and x = -5.

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The other one is solved the same way.

The solutions to it are x = 3 and x = 2

Edwin</pre