Question 1030211
 {{{(x^2 + 3x + 6)(x^2 + ax + b) = x^4 +(a+3)x^3 + (b+3a+6)x^2 + (3b +6a)x + 6b }}} after expansion.  This is supposed to be equal to {{{ x^4 + mx^2 + n}}} 

By equating coefficients, we obtain...
==> a+3 = 0,
m = b+3a+6,
3b+6a = 0, or b+2a = 0 after reduction,
6b = n

==> a = -3,
b = 6,
m = 6 - 9 +6 = 3, and 
n = 6*6 = 36

==> mn = 3*36 = {{{highlight(108)}}}.