a^2+b^2-8a+6b+25=0(a^2-8a+16)+(b^2+6b+9)=0(a-4)^2+(b+3)^2=0a=4b=-3(a^2+ab-6b^2)/(a^2-4ab+b)^2=(a+3b)(a-2b)/(a-2b)^2=(a+3b)/(a-2b)=(4-12)/(4+6)=-8/10=-0.8