Using numerical value of Solve

Question

Suppose I solve an equation y=Solve[x+3==8,x]

and I want to get the numerical value of y, how do I do that? I mean, if I want to work with my result and evaluate, for example y-2 it will not work, because y is not in the form of a number, but rather {{y->3}}. How can I convert it into a number?

Thanks

common pitfalls / Using the result of functions that return replacement rules — Kuba, Apr 27 '17 at 18:18

score 0 · Answer 1 · answered Apr 27 '17 at 18:01

0

In:

(* #1 *)
Solve[x + 3 == 8, x] // Part[#, 1, 1, 2] &
(* #2 *)
Last @@ Last @@ Solve[x + 3 == 8, x] 
(* #3 *)
x /. # & @@ Solve[x + 3 == 8, x]

Out:

5
5
5

answered Apr 27 '17 at 18:01

webcpu

3,182
12
17

1

Or y = Solve[x + 3 == 8, x][[1, 1, 2]] less typing :) – foxcode64 Apr 27 '17 at 18:15
Last @ Reduce[x + 3 == 8] – webcpu Apr 27 '17 at 18:30
No competition Uncharted, just pointing out that your first example can be shortened :) – foxcode64 Apr 27 '17 at 18:34
1

:) I know. It's just for fun. – webcpu Apr 27 '17 at 18:40
1

Okay then! Good to see someone with a passion for anonymous functions and the apply function, continue sir :) – foxcode64 Apr 27 '17 at 18:54
Solve[x + 3 == 8, x] /. {{_ -> n_}} -> n – webcpu Apr 27 '17 at 19:48

Using numerical value of Solve

1 Answers1