x+y^2=4

x^2+y^2=16

I set the first equation to x=4-y^2 then substituted it in the 2nd equation to get,

(4-y^2)^2+y^2=16 which I open up to:

(4-y^2)(4-y^2)+y^2=16 now when I try to FOIL I get stuck on the -y^2*-y^2

16-8y^2 ???? +y^2=16

is -y^2*-y^2 = y^4 ? or am I doing theis whole equation wrong?