nA  -> products 
n=integer → dCA(t)/dt =-k*CA(t)**n                        
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 depending on n: n=1,mono,n=2,bi,n=3,tri molecular reaction
 k  =reaction rate constant                                
 CA = Concentation of A as function of time :CA(t)         
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Eq(CA(t), Piecewise(((-C1*n + C1 + k*n*t - k*t)**(-1/(n - 1)), Ne(n, 1)), (nan, True)))
Eq(CA(t), Piecewise((C1*exp(-k*t), Eq(n, 1)), (nan, True)))
n=integer, dCA(t)/dt =-k*CA(t)**1
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Eq(CA(t), CA0*exp(-k*t))
n≠1, dCA(t)/dt =-k*CA(t)**n ,n=2
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1/(k*t + 1/CA0)
n≠1, dCA(t)/dt =-k*CA(t)**n ,n≠1
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Piecewise(((-C1*n + C1 + k*n*t - k*t)**(-1/(n - 1)), Ne(n, 1)), (nan, True))
list of symbols = [t, k, n, C1]
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analysis : Piecewise
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 Piecewise(((-C1*n + C1 + k*n*t - k*t)**(-1/(n - 1)), Ne(n, 1)), (nan, True))
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((-C1*n + C1 + k*n*t - k*t)**(-1/(n - 1)), Ne(n, 1))
(-C1*n + C1 + k*n*t - k*t)**(-1/(n - 1))
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find : C1,solve     
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 eq =  Eq((-C1*n + C1 + k*n*t - k*t)**(-1/(n - 1)), CA(t))
eq1 =  Eq((-C1*n + C1)**(-1/(n - 1)), CA(0))
eq2 =  Eq(C1, -(1/CA(0))**(n - 1)/(n - 1))
eq3 =  Eq((k*n*t - k*t + n*(1/CA(0))**(n - 1)/(n - 1) - (1/CA(0))**(n - 1)/(n - 1))**(-1/(n - 1)), CA(t))
eq4 =  Eq(CA(t), ((k*t*(n - 1)**2 + n*(1/CA(0))**(n - 1) - (1/CA(0))**(n - 1))/(n - 1))**(-1/(n - 1)))
check :solt = [Eq(CA(t), Piecewise(((-C1*n + C1 + k*n*t - k*t)**(-1/(n - 1)), Ne(n, 1)), (nan, True))), Eq(CA(t), Piecewise((C1*exp(-k*t), Eq(n, 1)), (nan, True)))]
 check ,n=2,reason see above 
eq5 =  False
 check ,n=1,reason see above 
eq6 =  False