Question

已知集合M={y|y=x²},N={y|y=x²+y²=4},则M∩N=

Answer 1

y=x²

x²+y²=4

y^2+y-4=0

1+16=17

y1=(-1+sqrt(17))/2

y2=(-1-sqrt(17))/2

所以M∩N={(-1+sqrt(17))/2,(-1-sqrt(17))/2}