You can put this solution on YOUR website! IF YOU ARE LOOKING FOR THE MISSING NUMBER FOR A PERFECT SQUARE THEN:
4X^2+12X+? MAKE THE TASK A LITTLE EASIER BY DIVIDING BY 4 THUS:
X^2+3X+(9/4) [1/2*9/4=3/2 & 2*3/2=3) THUS THE MISSING TERM IS (9/4)
(X+3/2)(X+3/2)