Can someone me with this question? this is josh's solution for the equation: x^2-6x-7=0 x^2-6x-7=0 x^2-6x=7 x^2-6x+9=7+9 (x-3)^2=16 x-3=16 x=19 x-3=-16 x=-13 is josh's solution correct? explain.

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?