Solving linear expression with syms

This is the symplification of the code I'm working on. I have 2 problems:

   1 - If you run this code, you will see that the matrix D has quite large 
       numbers. I would like to see those numbers simplified.
       (i.e. (1958266807048006347*a)/144115188075855872 becomes 13.5882*a)

   2 - After this, all I need is compute the X in A*X = b. 
       In this expression, A is a matrix where my entries containing an 'a' 
       are in the first column, the ones containing 'b' in the second and the 
       one containing 'c' in the third column. b is the vector containing all
       the entries without any 'a', 'b' or 'c'*.

syms a b c x y
func = a*log(x) + b*cos(x) + c*exp(x);
phi = (func - y)^2

dphida = diff(phi,a,1);
dphidb = diff(phi,b,1);
dphidc = diff(phi,c,1);

expand(dphida);
expand(dphidb);
expand(dphidc);

x1 = [0.24, 0.65,0.95, 1.24, 1.73, 2.01, 2.23, 2.52, 2.77, 2.99 ];
y1 = [0.23, -0.26, -1.10, -0.45, 0.27, 0.10, -0.29, 0.24, 0.56, 1.00];

for i=1:length(x1)
    A(i) = subs(expand(dphida),[x,y],[x1(i),y1(i)]);
    B(i) = subs(expand(dphidb),[x,y],[x1(i),y1(i)]);
    C(i) = subs(expand(dphidc),[x,y],[x1(i),y1(i)]);
end

A1 = sum(A(1,:));
B1 = sum(B(1,:));
C1 = sum(C(1,:));

D = [A1; B1; C1]

Answer 1

[Walter Roberson]

Use vpa() to convert the rational constants into fixed-point constants.