The equation for a circle with center (h, k) is (x - h)2 + (y - k)2 = r2. if a circle is modeled by the equation (x - 4)2 + (y + 6)2 = 49, what is the center of the circle? a) (4, 6) b) (4, −6) c) (−4, 6) d) (−4, −6)

Carbon- 14 is a radioactive form of carbon found in all living plants. after a plant dies, the carbon- 14 disintegrates. samples of similar living plants are used to determine the age of the remains. the amount of carbone-14 present after t years is given by the exponential equation n(t) = noe where no is the initial amount of carbon-14. the half-life of carbone-14 is 5600 years. charcoal from an ancient fire pit contains one third of earbon-14 found in similar living wood of the same size. find the age of the charcoal half-life is the time required for a quantity to reduce to half its initial amount