y²+3x=7,y³+x=3,求y等于几.

y²+3x=7,y³+x=3,求y等于几.
y²+3x=7,y³+x=3,求y等于几.

y²+3x=7,y³+x=3,求y等于几.
y²+3x=7 x=(7-y²)/3
y³+x=3 x=3-y³
(7-y²)/3=3-y³
3y³-y²-2=0
3y³-3y²+2y²-2=0
3y²(y-1)+2(y+1)(y-1)=0
(y-1)(3y²+2y+2)=0
3y²+2y+2=3(y+ 1/3)²+5/3恒>0,因此只有y-1=0 y=1
x=3-y³=3-1=2
y=1