How do you write an equation of a parabola witha focus and directrix?

Identify the initial amount a and the growth factor b in the exponential function. a(x)=680*4.3^x

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?

If log(a) = 1.2 and log(b)= 5.6, what is log(a/b)? a. 4.4b. 6.8c. not enough informationd. -4.4