m = 9;
t = linspace(-0.9,0.9,m)';
b = 1 ./ (1 + 25 * t.^2);
plot(t,b,'ro');
hold on;

A = [ones(m,1), t];
x = A \ b;
tvals = linspace(-1,1,1000);
plot(tvals, x(1) + x(2)*tvals, 'b-');

A = [ones(m,1), t, t.^2];
x = A\b;
plot(tvals, x(1) + x(2)*tvals + x(3)*tvals.^2); %,'g--');