get x values for given y from fit

I have data points x and y. I fit a 3rd order polynomial through these points. Now i want to find the x- values from the polynomial for

y = 0.00:0.05:14.00

This is the code for the fit:

x = [5965  7867  9459  11763  13881  14794  16000  16619  20000];
y = [3.7  6.34  7.04  7.89  8.61  8.91  9.25  9.42  10.19];

[p,~,mu] = polyfit(x,y,3);
y2 = polyval(p,x,[],mu);

plot(x,y,'o')
hold on
plot(x,y2)
hold off

please tell how to get a matrix with all the x-values for the given y-values. I'm new to matlab and clueless