解方程组{3x^2-2xy-y^2+4x+7y=13,4x+y=7
问题描述:
解方程组{3x^2-2xy-y^2+4x+7y=13,4x+y=7
答
3x^2-2xy-y^2+4x+7y=13 ① 4x+y=7 ②由②,得y=7-4x代入①中,得3x^2-2x(7-4x)-(7-4x)^2+4x+7(7-4x)=13整理,得5x^2-18x+13=0(x-1)(5x-13)=0x=1或x=13/5当x=1时,y=7-4=3当x=13/5时,y=7-52/5=-17/5原方程组的解为x=1,y=3...