How to do this. can you maybe show me your work?

What is the point-slope form of theequation for the line with a slope of-2 that passes through (1, 4)? a y + 1 = -2(x + 4)b y-1=-2(x-4)c y + 4 = -2(x + 1)d y - 4 = -2(x - 1)

Use the elimination method to solve the systems of equations.choose the correct ordered pair. 7x+4y=39

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?