1) a^4 + 16 + 17a^2 = (a^2 + 4)^2 - 1
2) x^2 - 10x + y^2 + 14y + 74 = (x - 5)^2 + (y + 7)^2 + 0
3) 2x^2 - 6xy + 9y^2 - 6x + 9 = (x - 3y)^2 + (y - 3)^2
4) x^2 - 4x - y^2 - 2y + 3 = (x - 2)^2 - (y + 1)^2 - 4
1) a^4 + 16 + 17a^2 = (a^2 + 4)^2 - 1
2) x^2 - 10x + y^2 + 14y + 74 = (x - 5)^2 + (y + 7)^2 + 0
3) 2x^2 - 6xy + 9y^2 - 6x + 9 = (x - 3y)^2 + (y - 3)^2
4) x^2 - 4x - y^2 - 2y + 3 = (x - 2)^2 - (y + 1)^2 - 4