已知ab互为相反数,cd互为倒数X=5(a-1)-2(a-3/2b),Y=C^2d+d^2-(d/c+c-6)求1/4(3x+y)-1/5(2x+3y)的值
问题描述:
已知ab互为相反数,cd互为倒数X=5(a-1)-2(a-3/2b),Y=C^2d+d^2-(d/c+c-6)求1/4(3x+y)-1/5(2x+3y)的值
答
a+b=0
cd=1
x=5a-5-2a+3b=3(a+b)-5=-5
y=c*cd+d²-d²-c+6=6
1/4(3x+y)-1/5(2x+3y)
=1/4(3*(-5)+6)-1/5(2*(-5)+3*6)
=1/4*(-9)-1/5*8
=-9*5/20-8*4/20
=-77/20你确定对吗?确定