b^2-8a+16/2b+6 : b^2-16/4b+12 |При b=2,4

(bˇ2-8b+16)/(2b+6) : (bˇ2-16)/(4b+12)=
=(b-4)(b-4)/2.(b+3) . 4(b+3)/b+4)(b-4)=
=2.(b-4)/(b+4)= (2b-4)/(b+4)

(2.2,4-4)/(2,4+4)=0,8/6,4=8/64=1/8=0,125