1. The problem statement, all variables and given/known data I'm having trouble with part b and part d, where there is some kind of ramp function involved http://img845.imageshack.us/img845/7507/76500775.jpg [Broken] 3. The attempt at a solution For part b, I calculated the gradient of that ramp, and the intercept which gives y = -x + 4, which would mean it's the function (t - 4) The other parts of the function are 2u(t-2) and -2u(t-4) ; which are the rise and fall respectively. So I multiplied (t-4) by these two and it's not the same graph: (t-4)*(2u(t-2)-2u(t-4) The solutions give (t-4)*(u(t-2)-u(t-4) - which now gives the correct graph. However, I don't understand why since it rises to 2u and drops by 2u, how did the constant two disappear? Also the equation here is simplified to 2u(t − 2) − r(t − 2) + r(t − 4) - which I do not understand as to where an r came from. Similarly for part d, I calculate the gradient and intercept, which gives y = -x for the slope, which gives the function (-t), and this shold be multiplied through like (-t)(u(t-1) - 2u(t-2)) I would have thought, but once again in the solution that 2 has disappeared from 2u(t-2) Can someone explain?