(60−3x)2+(80−3y)2=702(1)(60−5x)2+(80−5y)2=502(2){(60−3x)2+(80−3y)2=702(1)(60−5x)2+(80−5y)2=502(2)
Lấy 25.(1)-9.(2) ta được: 60-3,6x-4,8y=0⇔y=50−3x450−3x4
Thế vào (1) ta được: (60−3x)2+(80−3.50−3x4)2=702(60−3x)2+(80−3.50−3x4)2=702
⇔22516x2−6754x+20254=022516x2−6754x+20254=0
⇔ x=6⇒y=8