# second order differential systems of a non linear ODE

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Lewis Fer on 17 Jun 2021
Commented: Lewis Fer on 19 Jun 2021
Considering theth differential system equations to be solved are:
f''(t) = 3*f(t)*g(t) + 5 g''(t) = 4*g(t)*f(t) + 7 with initial conditions: f(0) = 1.5, g'(0) = 0 and boundary constraints tf = 1: g(1) = 3, f'(1) =q* f(1)
With q is natural number
how we can plot the solution satysfying the boundary conditions
Lewis Fer on 19 Jun 2021
in mathematic can we replace : f'(1) =q* f(1) by f'(1)=q*exp(q) ? because the solution of the differential equation
f'(x) =q* f(x) has the forme f(x)=C*exp(qx) and I know tha C in our case equal=1

Sulaymon Eshkabilov on 19 Jun 2021
Small typo err in your code:
xmesh = linspace(0,1,10);
sol = bvpinit(xmesh, @iguess);
sol = bvp5c(@odefcn,@bcfcn,sol,bvpset('RelTol ' ,1e-13 ,'AbsTol ',1e-13,'Nmax ',6000)); % ERR: No space after: 'RelTol', 'AbsTol', 'Nmax'
Lewis Fer on 19 Jun 2021
I fix it this err thank you Sulaymon Eshkabilov , and the main question how to do it if q=2 or 3 for example ?

R2015b

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