## use the "subs" command to subsitute equations for a variable

### Philosophaie (view profile)

on 20 Sep 2013

Here is a silly question: is there a way to use the "subs" command to subsitute equations for a variable?

```eqn = 2*(2*x-1) + 3*(3*x+2) + 4*(4*x-5)=11
eqn1 = subs(eqn, {2*x-1,3*x+2,4*x-5}, {a,b,c}); ???
```

The result:

```2*a+3*b+4*c=11 ???
```

Azzi Abdelmalek

### Azzi Abdelmalek (view profile)

on 20 Sep 2013

What is the aim of doing this?

Philosophaie

### Philosophaie (view profile)

on 20 Sep 2013

Simplify the viewing of large equation.

Walter Roberson

### Walter Roberson (view profile)

on 20 Sep 2013

It makes a difference as to whether the expressions appear exactly, or if instead you want an algebraic transformation. For example if the code had 2*x-2 and you substituted 2*x-1 -> a, then would you want the result to be a-1 or would you want the substitution to be skipped ?

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### Azzi Abdelmalek (view profile)

on 20 Sep 2013

```syms x a
y=2*(2*x-1);
subs(y,a)
```

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