I've used Wolfram Alpha for years, but I've never really understood how to type in complex formulas so that Wolfram Alpha can understand them.
Specifically, I struggle with telling Wolfram Alpha what certain variables stand for.
For example, I want to perform a sum of three numbers: x_1=3, x_2=4, and x_3=1.
But, when I type x_1 = 3, x_2 = 4, x_3 = 1, compute sum from i = 1 to 3 of x_i, which Wolfram Alpha correctly interprets as
I get the wonderful result
(What I was looking for was 3+4+1=8)
In other words, Wolfram Alpha understands my question and the information, but doesn't actually carry out the substitution to give me the answer I want.
Is there any way to force Wolfram Alpha to put in the substitution?
