Vector 3 LNK 2001 error

class Vector3
{
public:
	float x;
	float y;
	float z;

	Vector3();
	Vector3(float a, float b, float c);
};

Vector3::Vector3()
{
	x = 0;
	y = 0;
	z = 0;
}

Vector3::Vector3(float a, float b, float c)
{
	x = a;
	y = b;
	z = c;
}