# Numerical approximation for expression coefficients

 0 I currently have an equation that looks like x = 4/5(4y - 3)*z - 1/3 How can I get Sage to convert the coefficients to numerical approximations? I want to end up with something like x = 0.8(4y - 3)*z - 0.333333333 I tried x.n(), but that only gives a "cannot evaluate symbolic expression numerically" error. Also x*1.0 doesn't do anything. asked Apr 28 '11 Grover 3 ● 2 Kelvin Li 443 ● 10 ● 17 Since 1.2*x does what you want (well, except being multiplied by 1.2!), but not 1.0*x, I wonder if there is a bug here. See http://groups.google.com/group/sage-devel/browse_thread/thread/b6ab1e4499b07167# for a post about this on sage-devel. kcrisman (Apr 28 '11)

 2 If $x$ is to be treated as a polynomial, then the following might suit your needs: sage: var('y z') (y, z) sage: x = 4/5*(4*y - 3)*z - 1/3 sage: x.polynomial(RR) 3.20000000000000*y*z - 2.40000000000000*z - 0.333333333333333  Try sage: RR?  for more information about RR posted Apr 28 '11 Kelvin Li 443 ● 10 ● 17

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