3x-4y+5=0
3x-6=4y-11
3(x-2)=4y-11
x-2=(4y-11)/3
（x-2)的平方+(y+1)的平方
=(4y-11)^2/9+(y+1)^2
=(16y^2-88y+121)/9+y^2+2y+1
=(25/9)y^2-70/9 y+130/9
=25/9(y^2-14/5 y)+130/9
=25/9(y-7/5)^2-25/9*49/25+130/9
=25/9(y-7/5)^2+9
即当y=7/5时,最小值是+9.
此时x=1/5