Question

已知1/x+1/y=3 求值 1）x+y+3xy+3y^2/ 2xy+y^2 2）1/1-3x·1/1-3y

Answer 1

1/x+1/y=3

x+y=3xy

x+y+3xy+3y^2=3xy+3xy+3y^2=6xy+3y^2

x+y+3xy+3y^2/ 2xy+y^2=6xy+3y^2/2xy+y^2+3

1-3x·1/1-3y

=1-3x-3y+9xy=1-9xy+9xy=1

1/1-3x·1/1-3y

=1/1

=1