5x-5-3+3y+7-7y=12-27+3x

3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 (3x-4y)(5x-4y)-(7x-8y)(6y-5x) 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2) x^8-x^7y+x^6y^2-x^5y^3+x^4y^4-x^3y^5+x^2y^-xy^7+y^8 y-x=3 7x+5y=-9 {x+y=5{3x-7y=11 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) (7y-3x)-(8y-5x)= {y=x+3,7x+5y+9; x+y=3 x+2y=9 3/x+1=y y-x=3 y=2x-3 y-3x=1 2(x+1)-y=6 7x-5y=-9 7x-3y/5=5x-y/3-x+y/2 x-1/5=y+1/3 {2x+y/3-2y=0 2(2x+y)-5=7y