Is it possible to create a function which transforms one expression to another(by substitution)?

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Richárd Tóth 2019-7-23

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https://ww2.mathworks.cn/matlabcentral/answers/473069-is-it-possible-to-create-a-function-which-transforms-one-expression-to-another-by-substitution

编辑： Richárd Tóth 2019-7-23

The function would accept an input like y >= 2x + 2 and return something like 4ab - a - b + 2 <= 0 by using the following substitutions:

x=2*a* b

y = a+b

The substitution equation is fixed(more complex than this example), and the function should work for every kind of functions in the expressions, like x^4 or sin(x) etc.

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Answer 1

Steven Lord 2019-7-23

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https://ww2.mathworks.cn/matlabcentral/answers/473069-is-it-possible-to-create-a-function-which-transforms-one-expression-to-another-by-substitution#answer_384404

Use Symbolic Math Toolbox. The subs function will be of use to you.

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Richárd Tóth 2019-7-23

编辑：Richárd Tóth 2019-7-23

thanks, is there a function for moving everything to left side too(or right side if its >=)? So the expression will have the form: 4ab - a - b + 2 <= 0 instead of a+b >= 4ab + 2

Never mind, I found the solution, I just need to subtract rhs(expression), expression = expression - rhs(expression),

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