6x^2+14x+4
First factor out all numerical factors (=2 in this case)
2(3x^2+7x+2)
look for m,n such that m*n=3*2, m+n=7 => m=6, n=1
2(3x^2+6x + 1x+2)
Factor 3x^2+6x into 3x(x+2)
2( 3x(x+2)+1(x+2) )
factor out common factor (x+2)
2(x+2)(3x+1)
=>
6x^2+14x+4=2(x+2)(3x+1)