1.已知a.b互为相反数,c.d互为倒数,x=3(a-1)-(a-2b),y=c^2d+d^2-((d/c)+c-1)求(2x+y)/3-(3x-2y)/6的值

题目

1.已知a.b互为相反数,c.d互为倒数,x=3(a-1)-(a-2b),y=c^2d+d^2-((d/c)+c-1)求(2x+y)/3-(3x-2y)/6的值
2.(不)解方程组x+2y=5/2004 ,2y-x=2004/3试求代数式x^2-4y^2的值

答案

1、x=3(a-1)-(a-2b)=2a+2b-3=2(a+b)-3=-3y=c^2d+d^2-d/c-c+1=c(cd)+d(d-1/c)-c+1=c+d(d-d)-c+1=1(2x+y)/3-(3x-2y)/6=x/6+2y/3=-1/2+2/3=1/62、x+2y=5/2004 x-2y=-2004/3x^2-4y^2=(x+2y)*(x-2y)=5/2004 * (-2004/3)=-...