Solve[] does not return the solution to an easy system of equations

Question

I'm trying to solve the following system of equations:

gl1 = b == a - 1;
gl2 = b == 3;
Solve[{gl1, gl2}, {a}]

The solution set provided by Mathematica is empty {} - even though a -> 4 would be the correct solution.

I just reset the kernel, so I made sure that none of the variables used were already defined elsewhere.

What am I doing wrong?

Best regards Jan

Another 2 duplicates: https://mathematica.stackexchange.com/q/7668/1871 https://mathematica.stackexchange.com/q/6232/1871 — xzczd, Jan 27 '24 at 08:45

score 1 · Answer 1 · answered Jan 27 '24 at 08:31

1

May be you are looking for:

gl1 = b == a - 1;
gl2 = b == 3;
Simplify[gl1, gl2]

or

Eliminate[{gl1, gl2}, b]

a == 4

answered Jan 27 '24 at 08:31

Syed

score 0 · Answer 2 · answered Jan 27 '24 at 08:33

0

like this?

gl1 = b == a - 1;
gl2 = b == 3;
Solve[{gl1, gl2}, {a, b}]

{{a -> 4, b -> 3}}

answered Jan 27 '24 at 08:33

minhthien_2016

Do I need to include all the variables of my equations in the Solve function? Why isn't it working without the 'b'? – Jan E. Fromm Jan 27 '24 at 08:43
I think, gl1 and gl2 are two equations. – minhthien_2016 Jan 27 '24 at 14:30

2 Answers2