430.
=(7а-7(а-2б))/(а-2б)(а+2б)=
=(7а-7а+14б)/(а^2-4б^2)=
=14б/(а^2-4б^2)=14×3/(64-4×9)=
=42/(64-36)=42/28=3/2=1.5
431.
=(6а-3(2а-б))/(4а^2-б^2)=
=(6а-6а+3б)/(4а^2-б^2)=
=3б/(4а^2-б^2)=3×5/(4×25-25)=
=15/75=1/5
432.
=(2-81а^2+4+9а×9а)/18а=
=6/18а=1/3а=1/3×1/9=1/ 1/3=3