Luisa received $108 for a necklace she sold on an online auction. the auction site took fee of 10% of the selling price. what was the selling point of the necklace?

Ineed with question three. i don't understand how i'm supposed to achieve 3 marks.

Find the vertex for the parabola given by the function ƒ(x) = −3x2 − 6x.

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).