Which characteristics of a graph tell you that it represents a proportional relationship

I’m stuck on this i don’t understand.

Someone answer asap for ! michele pushes a box d meters across a floor. she uses a force f, in newtons, to push the box. she pushes the box for t seconds. the formula p = fd/t calculates the power, p, in watts, that it takes for michele to complete the task. solve the formula for d.

Use the quadratic function to predict f(x) if x equals 8. f(x) = 25x2 − 28x + 585