Which of the following equations shows how substitution can be used to solve the following system of equations? y = 2x + 3
2x + 5y = 3

2x + 5y = 2x + 3
2(2x + 3) +5y = 3
2x + 5(2x + 3) = 3
y = 3

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).