Question

若 √x-4 与 √4-y 互为相反数,求 xy 的算术平方根.

Answer 1

即,√(x-4)+√(4-y)=0,而√(x-4)≥0,√(4-y)≥0,∴x-4=4-y=0,x=y=4,√xy=√16=4