Question: nonlinear differential equation

hello my friends

I have a critical problem to solve below the system of differential equations

-(9/14)*R(t)^(19/14)-(285/196)*(diff(R(t), t, t))/R(t)^(9/14)+(2565/2744)*(diff(R(t), t))^2/R(t)^(23/14) = -k*(4*lambda+1/a(t)^3)

and R(t) = 6*((diff(a(t), t))^2/a(t)^2+(diff(a(t), `$`(t, 2)))/a(t))

I need to find form of a(t) numerically from set of differential equatios

plz help me as soon as possible

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