[a] Given the following data: xi Y; 1 1.25 1.5 1.75 5.10 N 5.79 6.53 7.45 8.46 Construct the least squares approximation of the form y-a ex, then find y(2.5). [b] Use best approximation for the first derivative to estimate f(0.75) for the function f(x)=x5-3x+1 with h-0.25, then find the absolute true error. [c] Use the Newton's method to estimate the maximum of the function f(x)=5 cos(x)- with initial guess x0=0.5. 6