Question

已知x2+xy=12,xy+y2=15,求（x-y)的负4次方乘以（x+y)的平方

Answer 1

x^2+xy=12,xy+y^2=15

x/y=4/5

y^2-x^2=3

(y-x)(y+x)=3

(x+y)=3/(y-x)

（x+y)^2/（x-y)^4

=9(x-y)^2=243