Does the relation y=x^2-1 defines y as a function of x

What is not true about kl and mn? what is mn? (show )

Cody was 165cm tall on the first day of school this year, which was 10% taller than he was on the first day of school last year.

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).