4k views

### Rewriting one expression using a variable representing another expression [duplicate]

I have two expressions: w1 = (a+b)/c^2; w2 = (a^3 + 3 a^2 b + 3 a b^2 + b^3)/c^6; How can I ask Mathematica to try to find an alternative expression for ...
• 23
193 views

### Rule can not work? [duplicate]

For example I have this equation,I want to use c->a/b ,but it can not work $$\frac{a^2}{b^2}+\frac{b^2}{a^2}+\frac{a}{b}+e^{a/b}+\frac{b}{a}+\log \left(\frac{a}{b}\right)$$ ...
• 1,572
3k views

### How to write a variable in terms of the other [duplicate]

I have an equation that defines a variable like y=4x+a. I had another equation, z=x+2+4, I would like to know if there is a way in Mathematica to get an expression in which z= a*y+C, in which a and C ...
409 views

### Rewriting the set of equations in terms of new variables, using replacement rules when the expression contains partial derivatives [duplicate]

I am working with cumbersome equations, that contain a lot of terms. Here I will consider simple example: ...
190 views

### ReplaceAll with Powers [duplicate]

If I run the following code: a^2/b^2 /. {a/b -> c} I'm getting output: a^2/b^2 How can I obtain ...
• 33
836 views

### Replacing a expression in another expression with a Variable [duplicate]

I want to set a symbol (or variable) for an expression. Here is an example: A x^2 + C x + D I want to reduce this expression to ...
• 1
198 views

### How can I use ReplaceRepeated (//.) in this case? [duplicate]

Consider the following case: (a^3*b) //. {a^2 -> c, a*b -> d} instead of c d the output is: ...
• 6,757
1 vote
173 views

### Reverse substitution [duplicate]

If you apply rules and then simplify you may get something like. (25 A^2 hbar Sqrt[π])/Sqrt[hbar m w] How would you get mathematica to rewrite this in terms of E ...
• 991
313 views

### How can I simplify the result of a differential equation by using my own defined expressions? [duplicate]

I want to solve the following differential equation with mathematica: α β * w''''''[ξ] + ( 1 + α - p ) * w''''[ξ] + p/β * w''[ξ] = 0 The answer seems at ...
• 45
59 views

### How to replace polynomials numerically? [duplicate]

We know that the value of this equation is 0 x2 y1 - x1 y2 == 0 For the following equation, there is a correlation between the polynomial parts of the known ...
• 4,523
1 vote
149 views

### Introducing new variables implicitly [duplicate]

I have a calculation expr111 = cs[giso, xiso, 1, 1, 1] that gives the result -((k x)/(2 (1 + 1/4 k (x^2 + y^2 + z^2)))) I ...
• 11
1 vote
114 views

### How do I format expressions so that replacement rules correctly apply to exponents? [duplicate]

I have a series of rules that I would like to apply to a series of expressions with variables, but cannot get Mathematica to correctly recognize that these rules should apply when my variables have ...
• 11
1 vote
114 views

### Solving for a constant multiplier of a variable [duplicate]

I would like to make this manipulation: Solve[r Sin[α[t]] + l Cos[ϕ[t]] Sin[γ[t]] == 0, l*Cos[ϕ[t]]] But it seems that the ...
• 1,099
109 views

### Substitution inside an expression [duplicate]

I'm trying to get mathematica to replace an expression with a reduced form. I wanted to replace $(k/w)$ with $h$ in a particular expression, and I've tried something like: ...
• 877
Say I have an expression $a+b+a\times b$ and I define $c:= a\times b$. How do I get Mathematica to write $a+b+a\times b$ in terms of $c$, i.e. $a+b+c$?