Question

已知x分之一加y分之一等于5,xY等于负一,则x得四次方分之一加y的四次方分之一等于?

Answer 1

(1/x+1/y)^2=25

1/x^2+2/xy+1/y^2=25

1/x^2+1/y^2=27

(1/x^2+1/y^2)^2=729

1/x^4+1/y^4+2/x^2y^2=729

1/x^4+1/y^4=727