How To find The x intercept

I;m trying to find all of the x intercepts of an ODE of my plot below.

This is my code

Fmax = 0.7e-9; rh = 0.97e-9; rt = 0.31e-9;
B = 1.4e-19; rs = 0.51e-9; G = 1.8e-11;
S = -1.0e-4; Vm=0.45; D = 5.0e-14;
Kb = 1.38e-23; T = 310.0;
r=[10E-10:1E-08:10E-07]
y1 = Vm*Vm*Fmax./(1.0+rh./(r+rt));
y2 = 4.0*B*(rs^4)./(r.^5);
y3 = -2.0*pi*G;
y4 = 2.0*pi*S*r;
m = D/(Kb*T);
drdt = m*(y1+y2+y3+y4);
figure
plot(r,drdt)
xlabel('R (nm)')
ylabel('dr/dt (nm with respect to time in seconds)')
legend('Vm=0.45')

How do I find the x-intercepts and how do I expand the range so I can see the entirety of the plot?

[darova]

What about fsolve? polyxpoly?

Answer 1

[Srivardhan Gadila]

Refer to Specify Axis Limits and specify the limits for X and Y axis.