已知：a、b互为相反数,cd互为倒数x=7(a-1)-2(a-2/5b),y=c^2d+d^2-(d/c+c-3）,求2x-y/3-3x+2y/6的值.

Question

已知：a、b互为相反数,cd互为倒数
x=7(a-1)-2(a-2/5b),y=c^2 d+d^2 -(d/c +c-3）,求2x-y/3 - 3x+2y/6 的值.

Answer 1

因为a,b是相反数,所以a+b=0
x=7(a-1)-2(a-2/5b)=7a-7-2a+4/5b=5a-4/5a-7=21/5a-7
c,d是倒数,cd=1
y=c^2 d+d^2 -(d/c +c-3）=c*1+d^2-(d/(1/d)+c-3)=c+d^2-d^2-c+3=3
2x-y/3 - 3x+2y/6=-x=7-(21/5) a
我感觉题目很有问题.