## 15359 Reputation

12 years, 100 days

## Brackets...

Replace the square brackets by round brackets:

(24+24*beta[1]*x+24*beta[2]*x^2+24*beta[3]*x^3+24*beta[4]*x^4)+(2*(beta[1]+2*beta[2]*x+3*beta[3]*x^2+4*beta[4]*x^3))*(-24+24*x)+(2*beta[2]+6*beta[3]*x+12*beta[4]*x^2)*(12-24*x+12*x^2)-L^4*m[0]*Omega^2*(-(1/2)*x^2-R*x+R+1/2)*(12-24*x+12*x^2)/EI[0]-F*L^2*(12-24*x+12*x^2)/EI[0]-L^4*m[0]*Omega^2*(-x-R)*(12*x-12*x^2+4*x^3)/EI[0]-L^4*m[0]*omega^2*(6*x^2-4*x^3+x^4)/EI[0];

collect(%, x);

## Solution...

To solve the problem you need to determine the values ​​of all the parameters, specify the initial conditions and assign names to the found solutions.

Example:

restart;

x, y, m, n:=1, 2, 3, 4:

sol:=dsolve({(D(a))(t) = x-y*a(t), (D(b))(t) = m*a(t)-n*b(t), a(0)=0, b(0)=0.5}, {a(t), b(t)});

a:=unapply(rhs(sol[1]), t);

b:=unapply(rhs(sol[2]), t);

plot(60/0.98 * a(t)*b(t), t=0..10, labels=["t", "h(t)"]);

## More generally...

In my code, I relied on your formula, in which the number  n  determines the size of the segment of the boundary value problem and the number of parts into which divided this segment. If we divide these two parameters, we obtain a slightly more general problem. The number  theta can also be considered discretely as in your formula, and it can more accurately be considered by the integral, if your last formula to the limit as  n  tends to infinity. In the example below 0.001 step corresponds to the division of the interval from 0 to 3 per 3000 parts:

restart;

a:=3:  n:=3000:

ode:=diff(T(x),x\$2)-T(x)^2=0;

bc:=T(0)=1,T(a)=0;

V:=dsolve({ode, bc}, numeric):

AverageT:=evalf(Int(x->rhs(V(x)[2]), 0..a))/a;

`T`:=[seq(rhs(V(x)[2]), x=a/n..a, a/n)]:

Int_theta:=evalf(sqrt(Int(x->(rhs(V(x)[2])-AverageT)^2, 0..a)/a)/AverageT);

If   increases, the theta will be close to  Int_theta .

## Solution...

restart;

n:=3:

ode:=diff(T(x),x\$2)-T(x)^2=0;

bc:=T(0)=1,T(n)=0;

V:=dsolve({ode, bc}, numeric);

AverageT:=evalf(Int(x->rhs(V(x)[2]), 0..3))/n;

`T`:=[seq(rhs(V(x)[2]), x=1..3, 1)];

## Solution...

Solution by substitution  x-1=t^2 :

eq1:=sqrt(x+3-4*sqrt(x-1))+sqrt(x+8-6*sqrt(x-1))=1:

eq2:=x-1=t^2:

simplify(algsubs(eq2, eq1)) assuming t>=0;

sol:=solve(%);

L:=convert(sol, list);

x:=unapply(solve(eq2, x), t);

RealRange(x(L[1]), x(L[2]));  # All roots of the initial equation

Of course, after the equation is solved with respect to  t , it is easier to solve it by hand for  x , using the equality x=1+t^2

## Solution with DirectSearch package...

On the solution of discrete optimization problems, see ?DirectSearch[Search].

Solution of the problem:

The example shows that the solution of such problems with DirectSearch package is not effectively.

integer.mw

## Solution...

Your problem is easily solved by exhaustive search. Denoted by  a, b, c, d, e, f, g, h  vertices of the cube:

Code:

L:=combinat[permute]({seq(i^2, i=1..8)}):

n:=infinity: S:={}:

for i in L do

a, b, c, d, e, f, g, h := i[1], i[2], i[3], i[4], i[5], i[6], i[7], i[8]:

m := a*b+b*c+c*d+a*d+a*e+b*f+c*g+d*h+e*f+f*g+g*h+e*h: S:=S union {m}:

if m<n then n:=m:

M:=[m, ["a"=a, "b"=b,"c"= c, "d"=d, "e"=e, "f"=f, "g"=g, "h"=h]]:  fi:

od:

S:  # The set of all possible values of this sum

nops(S);

max(S);

min(S);

M;

622

9420

3586

[3586, ["a" = 1, "b" = 36, "c" = 9, "d" = 64, "e" = 49, "f" = 16, "g" = 25, "h" = 4]]

## Maple help...

For details see  ?rtable_indexing

## Possible variant...

f := 1/3 + x/5:

numer(f)/convert(denom(f), symbol);

There are a few extra parentheses and if..end if also not necessary:

aprcos:=proc(x,n::nonnegint)

local resp, i;

resp:=0;

for i from 0 to n do

resp:=resp+(-1)^i*x^(2*i)/(2*i)!;

end do;

resp;

end proc;

## Re...

c:=Array([1, 3, 5, 7, 8, 2, 1]):

ArrayNumElems(c);

7

## Two solutions: n=522 or n=2004...

We have a Diophantine equation  4^27+4^1016+4^n=m^2. Rewrite it as follows

4^1016+4^27=(m-2^n)*(m+2^n)

Hence we find that  2^n<4^1016+4^27 .  Should be n <2033, as

is(2^2033>4^1016+4^27);

true

So it is enough to make exhaustive search for  n  from 1 to 2032:

L:=[]:

for n from 1 to 2032 do

m:=sqrt(4^27+4^1016+4^n):

if type(m, integer) then L:=[op(L), n]:  fi:

od:

L;

[522, 2004]

## Another simple way...

plot3d(5, x = -3*Pi .. 3*Pi, y = (1/2)*sin(x) .. (1/2)*sin(x)+4, color = white, filled = true, scaling = constrained, grid = [50, 11], orientation = [93, -14, -23], axes = none, lightmodel = light1);

## Simple way...

plot3d(5, x = -3*Pi .. 3*Pi, y = (1/2)*sin(x) .. (1/2)*sin(x)+4, color = white, filled = true, scaling = constrained, numpoints = 2500, orientation = [93, -14, -23], axes = none, lightmodel = light1);

## Manual solution...

Unfortunately, Maple cannot cope with this task:

assume(m, posint, n, posint):

is((2*m-1)^(2^n)-1 mod 2^(n+2) =0);

FAIL

But the problem is easily solved manually by induction, if we use the identity

(2*m-1)^(2^(n+1))-1=( (2*m-1)^(2^n)-1 )*((2*m-1)^(2^n)+1)

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