Выразить x через y: 1) у^2=4x-x^2 2) y=x-x^2 3) y=(2x-x^2)^(1/2)

Y²=4x-x²-4+4
y²=4-(x-2)²
(x-2)²=4-y²
x-2=√(4-y²)
x=(√(4-y²))+2

y=x-x²+1/4-1/4
y=1/4-(x-1/2)²
(x-1/2)²=1/4-y
x-1/2=√(1/4-y)
x=(√(1/4-y))+1/2