Is it possible to simplify symbolic expressions with known relations

Say I have some arbitrary symbolic expressions

syms x1 x2
% x1*x2 == 1
a = x1*x2 + x1*x2;
b = 2*a

If it is known that x1 * x2 == 1 is it possible to have matlab actively simplify based off of that relation so that b returns the answer 4 without the use of subs?

Answer 1

[Star Strider]

I assume (link) it would!

syms x1 x2
assume(x1*x2 == 1)
a = x1*x2 + x1*x2;
b = 2*a

producing:

b =
4*x1*x2

[rooo000]

Haha! Very much appreciated thank you.

[Star Strider]

As always, my pleasure!

Answer 2

[Stephan]

Hi,

use assume - like Star Strider suggested and additionally use simplify to get the desired result;

syms x1 x2
assume(x1*x2 == 1)
a = x1*x2 + x1*x2;
b = 2*a;
b = simplify(b)

result:

b =
 
4