x.f and x.q

That difference is 999....

In the top half, you solve an ODE, resulting in a function y(x).

You plot that function for values of x ranging from 0 to x.f

where x.f is defined as being 1000.

In the bottom half, the following problem is solved :

For which value of x is it that y(x)=1000 ?

You start with a guess value x.g set to 1.

Once found it appears to be 29.734, as shown by find(x.q)=29.734

You did not assign the result of the find() to anything, so

x.q is still 1, and the difference between x.f and x.q is 1000-1=999.

Success!
Luc

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