Optimization package

Hi there,

I have a complex math equation which does not have a closed form solution.
It is -

y <- (p*exp(-a*d)*(1-exp((d-p)*(a-x[1]))))/((p-d)*(1-exp(-p*(a-x[1]))))

For this equation, I have all the values except for x[1]. So I need to solve
this problem numerically. Can anyone suggest an optimization package that I
can use to estimate the value for x[1]?

Thanks in advance,

Diviya

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