x^2/16+y^2/4=1|*16
x^2+4y^2=16
4y^2=16-x^2
y^2=(16-x^2):4
y=+-sqr((16-x^2):4)
y=+-sqr(16-x^2):2
y=+-sqr((4-x)(4+x)):2
x^2/16+y^2/4=1|*16
x^2+4y^2=16
4y^2=16-x^2
y^2=(16-x^2):4
y=+-sqr((16-x^2):4)
y=+-sqr(16-x^2):2
y=+-sqr((4-x)(4+x)):2