已知a b互为相反数,x y互为倒数,且ab均不为0,则代数式7xy(a+b)-3(xy)^2+2a/b的值为

Question

如题所述

Answer 1

解：a, b互为相反数，则 a+b=0；a，b均不为0，则 a/b=-1
x, y互为倒数，则 xy=1

7xy(a+b)-3(xy)²+2a/b
=7×1×0-3×1²+2×(-1)
=0-3-2
=-5

Answer 2

a+b=0，a=-b
xy=1
∴7xy(a+b)-3(xy)²+2a/b
=7×1×0-3×(1)²+2×(-b)/b
=0-3-2
=-5