# I want to solve this equation. please help me

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kumar sourabh on 9 Oct 2018
Commented: Alex Sha on 20 Dec 2019
3.8 = a (1 - exp(b×8.2)) + c (exp(d×8.1) - 1);
27.9 = a (1 exp(b×63)) + c (exp(d×35.667) - 1);
23.5 = a (1 - exp(b×59.5)) + c (exp(d×59.5) - 1);
13.7 = a (1 - exp(b×35.7)) + c (exp(d×35.7) - 1)};

madhan ravi on 9 Oct 2018
syms a b c d
eq1 = 3.8 == a*(1 - exp(b*8.2)) + c*(exp(d*8.1) - 1);
eq2 = 27.9 == a*(1 - exp(b*63)) + c*(exp(d*35.667) - 1);
eq3 = 23.5 == a*(1 - exp(b*59.5)) + c*(exp(d*59.5) - 1);
eq4 = 13.7 == a*(1 - exp(b*35.7)) + c*(exp(d*35.7) - 1);
[a,b,c,d]=vpasolve(eq1,eq2,eq3,eq4,a,b,c,d)
madhan ravi on 11 Oct 2018
Thank you once again @sir Walter.

Alex Sha on 19 Dec 2019
Here is the right solution, obtained from 1stOpt:
a: -2.38880243947768E-9
b: 0.357245116257183
c: -32.3471147348507
d: -0.0154282661155712
Alex Sha on 20 Dec 2019
Hi, for "(a*(exp((41*b)/5) - 1) - c*(exp((81*d)/10) - 1) + 19/5)^2 + (a*(exp((119*b)/2) - 1) - c*(exp((119*d)/2) - 1) + 47/2)^2 + (a*(exp((357*b)/10) - 1) - c*(exp((357*d)/10) - 1) + 137/10)^2 + (a*(exp(63*b) - 1) - c*(exp((35667*d)/1000) - 1) + 279/10)^2", the minmum value：
Objective Function (Min.): 1.67130234831156E-23
a: -2.38880243946672E-9
b: 0.357245116257267
c: -32.347114734847
d: -0.015428266115563