Question

1.已知y/x=3,求x+y/x-y 2.已知X=根号3+1,y=根号3-1,求XX-YY/XXY+XYY

Answer 1

(x+y)/(x-y)

= (x/x+y/x)/(x/x-y/x)

= (1+y/x)/(1-y/x)

=(1-3)/(1+3)

=-2/4

=-1/2

x=√3+1,y=√3-1

(x^2-y^2)/(x^2y+xy^2)

=(x+y)(x-y)/[xy(x+y)]

=(x-y)/(xy)

=(√3+1-√3+1)/(√3+1)(√3-1)

=2/2

=1

Y为正数

y=x^2/(2-3x)

x^2/(2-3x)>0

(2-3x)>0

x