Posted by Nathan on Monday, April 9, 2012 at 9:34am.
Factor over {complex numbers}
9x^2 + 49

Math  Reiny, Monday, April 9, 2012 at 10:01am
how about ...
(3x + 7i)(3x  7i) ?
check:
(3x + 7i)(3x  7i)
= 9x^2 49i^2, but i^2= 1
= 9x^2  49(1)
= 9x^2 + 49