Present value, PV = $500
Future value, FV = 2*PV = 2*500 = $1,000
Rate, r = 4% = 0.04
Compounding times in a year, n = 4 (compounded quarterly)
Time, t = ??
The future value expression is stated as:
FV = PV (1+r/n)^nt
Substituting;
1000 = 500 (1+0.04/4)^4t
2 = (1.01)^4t
ln 2 = 4t ln 1.01
0.6931 = 4t* 0.00995
0.6931 = 0.0398t
t = 17.414 years
Time required for the amount to double is 17.41 years.
First, recall that Gaussian quadrature is based around integrating a function over the interval [-1,1], so transform the function argument accordingly to change the integral over [1,5] to an equivalent one over [-1,1].



So,

Let

. With

, we're looking for coefficients

and nodes

, with

, such that

You can either try solving for each with the help of a calculator, or look up the values of the weights and nodes (they're extensively tabulated, and I'll include a link to one such reference).
Using the quadrature, we then have
