We want to find delta F, so we're going to have F of our X not, which is 4 plus our DX, which is .1 -, F of four. So literally we're just going to figure out what F of 4.1 is minus F of four. Putting 4.1 in cubing it -4.1 minus the quantity of 4 ^3 -, 4 is going to give us 4.821. Our DF. It tells us it's just F prime at X, not DX. So our F prime is going to be three X ^2 -, 1. Our DX was given as .1, so we're going to put X as four and DX as .1 and get 4.7. Part C says find the approximation error. The approximation error is just the absolute value of the change of F minus the differential in terms of F So delta F minus DF 4.821 -, 4.7 or one point .121.