a-maths!!!!!!

Let G(x,y) be the centre
distant between G and C = distant between G and the equation "x-2y+3=0"
√(x+1)² + (y-2)² = (x-2y+3) / √(1²+2²)
√5 √(x² + y² + 2x - 4y + 5) = x - 2y + 3
5x² + 5y² + 10x - 20y + 25 = (x - 2y + 3)²
5x² + 5y² + 10x - 20y + 25 = x² - 4y²- 4xy + 6x - 12y + 9
4x² + 9y² + 4x - 8y + 4xy + 16 = 0