If r = x y 1 1 0 g and A = 0 1 f g f c show that r^T Ar = 0 is the equation of the circle in R^2 with centre (−g, −f) and radius square root(g^2 + f^2 − c).

Which of the following questions describes the equation g + (-4) = -5? a)what number, when added to negative four, is equal to negative five? b)what number, when added to negative five, is equal to negative four? c)what number, when subtracted from negative four, is equal to negative five? d)what number, when subtracted from negative five, is equal to negative four?