document.write( "Question 1128653: Hi can you plz help me with this qs? I didn't know under which section to post it so im posting it here:
\n" ); document.write( "the curve y = ax^3 + bx^2 + cx + d has a gradient of -3 at (0, 15/2) and a turning point at (3,6). Find a,b,c,d
\n" ); document.write( "
\n" ); document.write( "

Algebra.Com's Answer #745144 by greenestamps(13200)\"\" \"About 
You can put this solution on YOUR website!


\n" ); document.write( "y = ax^3+bx^2+cx+d
\n" ); document.write( "y' = 3ax^2+2bx+c
\n" ); document.write( "y'' = 6ax+2b

\n" ); document.write( "The given information tells us...

\n" ); document.write( "y(0) = 15/2 --> c = 15/2 (1)
\n" ); document.write( "y(3) = 6 --> 27a+9b+3c+d = 6 (2)
\n" ); document.write( "y'(0) = -3 --> c = -3 (3)
\n" ); document.write( "y''(3) = 0 --> 18a+2b = 0 (4)

\n" ); document.write( "Substitute (1) and (3) in (2):

\n" ); document.write( "27a+9b-9+15/2 = 6
\n" ); document.write( "27a+9b = 15/2
\n" ); document.write( "18a+6b = 5 (5)

\n" ); document.write( "Subtract (4) from (5):

\n" ); document.write( "4b = 5
\n" ); document.write( "b = 5/4 (6)

\n" ); document.write( "Substitute (6) in (4):

\n" ); document.write( "18a+5/2 = 0
\n" ); document.write( "a = -5/36

\n" ); document.write( "The polynomial is

\n" ); document.write( "\"%28-5%2F36%29x%5E3%2B%285%2F4%29x%5E2-3x%2B%2815%2F2%29\"

\n" ); document.write( "A graph...

\n" ); document.write( "
\n" ); document.write( "
\n" );