# How to solve max load of P in Matlab?

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Katie on 20 Mar 2013
The equations governing the forces on the beam shown below are as follows:
F_ax=0
P=F_ay+F_by
P=(5.*F_by)./10
We want to determine the maximum load, P, which will result in a load at the roller, F_by, which does not exceed 500 lb.
Write a Matlab program which uses the above system of equations to determine the maximum force P which results in vertical force on the roller, F_by of between 499 lb and 500 lb. Your approach should repetitively solve the above system of equations until the desired result is obtained.
This is the code I have, but I don't know where to go next:
F_ax=0
F_by<=500 %lbs
F_by>=499 %lbs
P=F_ay+F_by
P=(5.*F_by)./10

bym on 21 Mar 2013
So, when I see a problem statement that says "solve the above system of equations" I think of formulating the equations in matrix form. The coefficient matrix for the equations involving P is
c =
1.0000 1.0000
0 0.5000
when I see a problem statement that says "... until the desired result is obtained", I think of a loop structure
doc while
when the problem statement says "[repetitively] solve..." The repetition is taken care of in the loop, but solving usually involves finding the unknowns. this often involves mldivide
doc mldivide
As you can see, I haven't given you the direct answer, but areas to explore in solving your homework problem
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bym on 22 Mar 2013
doc command is just a way of getting to the help documentation from the command line. As far a getting the coefficient matrix, it is a matter of writing out the equations and putting the coefficients into a matrix, e.g.
1*F_ay+1*F_by = P
0*F_ay+.5*F_by = P
equals
[1,1;0,.5]*[F_ay;F_by] = [P;P]