Write it as y^2=1-x^2
Learn the following steps because they would apply whatever the question.
1 Replace x by 2x (so x^2 becomes (2x)^2=4x^2
2 We need the 3 times the expression for y ( so y^2 will get multiplied by 9)
3 Replace x by (x-1)
4 Replace y by (y+4)