# Tag Info

## Hot answers tagged expression-manipulation

13

You can use Series to specify the order of approximation. When an expression involving the output of Series, which is a SeriesData object, is evaluated, the calculus is done for you. sol = Solve[x^2 + (b + Epsilon)*x + c == 0, x] approx = sol /. Epsilon -> Series[Epsilon, {Epsilon, 0, 1}] // Normal Alternatively, you could apply Series to the ...

9

Well, the following meets your formal requirements evenFunction[f_][args__] := f[Abs /@ Unevaluated[args]] evenFunction[even][a, b, c] even[Abs[a], Abs[b], Abs[c]] But is it really better than evenFunction[f_][args__] := f @@ Abs[{args}] I, myself, would choose the 2nd version over the 1st. Update It is not necessary to set the attribute ...

5

You don't say explicitly how you want to handle terms of order zero. Assuming that these are also to be discarded expr = a x^3 + b x^2 + c x + d; minOrder = 2; coefList = CoefficientList[expr, x]; lenCoefList = Length[coefList]; Expand[(Expand[x*expr] /. ((x^n_ /; n > minOrder) -> $t^n) /. {x -> 0,$t -> x})/x] (* b x^2 + a x^3 *) ...

4

If you first SetOptions[Series, Analytic -> False] and then wrap f[x] in HoldForm, Series[HoldForm[f[x]]*Sin[x],{x,0,3}] then when you take this output and run it as an input, HoldForm[f[x]] is not expanded out.

3

You can executive the code in mma 10 or above version EntityClass["WolframLanguageSymbol", "Atomic"]//EntityList But is not all atomic function,as I know.

2

Normal@Series[your expression,{x,0,1}]

2

Defining a function like Clear[FactorByVariable] FactorByVariable[p_,c_]:=c Expand[p/c] will be one of the simpler options. The argument p is the polynomial you wish to factor from and c is the variable you wish to factor out. I think the reason you can't get your desired result with something like FactorTerms[a x + b x^2 + c x^3,{a,c,x}] is because ...

1

Convert both variables to the same, then evaluate as a series from infinity should work in most cases: A straightforward example for some function f = f(x,y): Series[f/.{x->q,y->q},{q,Infinity,2}] Of course this requires that both variables grow parametrically at the same rate. This also allows you to take different limits: x->1/q for example ...

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