4x^2+12x+9-16=4x^2+2xa+2xb+ab /-4x^2
12x-7=2x(a+b)+ab
12x=2x(a+b) /:2x =>
a*b= -7
a+b=6 => a=6-b
a*b= -7 => (6-b)*b=-7 => 6b-b^2=-7
b^2-6b-7=0
Delta=rad(36+28)=rad(64)=8
b1=(6+8)/2=7
b2=(6-8)/2= -1
b=7 => a=6-7=-1 => a+b=6
b= -1 => a=6+1=7 => a+b=6
Asadar suma numerelor a si b este 6.
Succes!
