document.write( "Question 1195206: If x+2 and x-3 are factors of the polynomial\"p%28x%29=x%5E3%2B5x%5E2%2Bax%2Bb\", find a. \n" ); document.write( "
Algebra.Com's Answer #827640 by greenestamps(13200)\"\" \"About 
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\n" ); document.write( "You have already received four responses, all showing different ways to solve the problem.

\n" ); document.write( "Here is yet another way that might teach you something useful.

\n" ); document.write( "In a cubic equation with leading coefficient 1,

\n" ); document.write( "\"x%5E3%2Bbx%5E2%2Bcx%2Bd=0\"

\n" ); document.write( "with roots p, q, and r, the following are the relationships between the roots and the coefficients of the equation:

\n" ); document.write( "(1) b = -(p+q+r)
\n" ); document.write( "(2) c = (pq+pr+qr)
\n" ); document.write( "(3) d = -(pqr)

\n" ); document.write( "Note it is easy to see these relationships by writing the polynomial equation in factored form and expanding:

\n" ); document.write( "\"%28x-p%29%28x-q%29%28x-r%29=x%5E3%2B%28-p-q-r%29x%5E2%2B%28pq%2Bpr%2Bqr%29x-pqr\"

\n" ); document.write( "To use these facts to solve this problem....

\n" ); document.write( "Since x+2 and x-3 are factors of the polynomial, two of the roots are p=-2 and q=3.

\n" ); document.write( "The coefficient of the x^2 term is 5, so from (1) above
\n" ); document.write( "\"-%28p%2Bq%2Br%29=5\"
\n" ); document.write( "\"-%28%28-2%29%2B%283%29%2Br%29=5\"
\n" ); document.write( "\"-%281%2Br%29=5\"
\n" ); document.write( "\"1%2Br=-5\"
\n" ); document.write( "\"r=-6\"

\n" ); document.write( "So the third root is r=-6.

\n" ); document.write( "The problem asks for the coefficient of the x (linear) term. From (2) above, the coefficient of the linear term is

\n" ); document.write( "\"a=pq%2Bpr%2Bqr=%28-2%29%283%29%2B%28-2%29%28-6%29%2B%283%29%28-6%29=-6%2B12-18=-12\"

\n" ); document.write( "ANSWER: a = -12

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