document.write( "Question 410986: Use the quadratic formula to solve the following equation for x, show as much work as possible: 0 = 2x2 - 5x - 18.
\n" ); document.write( "
\n" ); document.write( "

Algebra.Com's Answer #288897 by jsmallt9(3758)\"\" \"About 
You can put this solution on YOUR website!
Please use the \"^\" symbol (SHIFT+6) to indicate exponents. \"2x2\" could be interpreted as 2 times x times 2.

\n" ); document.write( "The general quadratic equation is:
\n" ); document.write( "\"ax%5E2+%2B+bx+%2B+c+=+0\"
\n" ); document.write( "You must learn this because the Quadratic Formula:
\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28b%5E2+-+4ac%29%29%2F2a\"
\n" ); document.write( "is written in terms of the a, b and c from the genreal equation.

\n" ); document.write( "With your equation
\n" ); document.write( "\"0+=+2x%5E2+-+5x+-+18\"
\n" ); document.write( "a = 2
\n" ); document.write( "b = -5
\n" ); document.write( "c = -18
\n" ); document.write( "(If you don't see why b and c are negative, then look at the general equation. It is written with additions. So you have to write (ar least think of) your equation with additions: \"0+=+2x%5E2+%2B+%28-5x%29+%2B+%28-18%29\"

\n" ); document.write( "Now we just substitute these values into the formula and simplify:
\n" ); document.write( "\"x+=+-%28-5%29+%2B-+sqrt%28%28-5%29%5E2+-+4%282%29%28-18%29%29%29%2F2%282%29\"
\n" ); document.write( "which simplifies as follows:
\n" ); document.write( "\"x+=+%28-%28-5%29+%2B-+sqrt%2825+-+4%282%29%28-18%29%29%29%2F2%282%29\"
\n" ); document.write( "\"x+=+%28-%28-5%29+%2B-+sqrt%2825+%2B+144%29%29%2F2%282%29\"
\n" ); document.write( "\"x+=+%28-%28-5%29+%2B-+sqrt%28169%29%29%2F2%282%29\"
\n" ); document.write( "\"x+=+%285+%2B-+sqrt%28169%29%29%2F4\"
\n" ); document.write( "\"x+=+%285+%2B-+13%29%2F4\"
\n" ); document.write( "Quadratic equations have two solutions. The \"plus or minus\" symbol in the formula is a shorthand way of expressing both solutions within the same expression. It is now time to write the two solutions separately. This last expression is a shorthand way of saying:
\n" ); document.write( "\"x+=+%285+%2B+13%29%2F4\" or \"x+=+%285+-+13%29%2F4\"
\n" ); document.write( "We can now continue with the simplifying:
\n" ); document.write( "\"x+=+18%2F4\" or \"x+=+%28-8%29%2F4\"
\n" ); document.write( "\"x+=+9%2F2\" or \"x+=+-2\"
\n" ); document.write( "
\n" );