Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
j
-
1
i
=
0
x
*
y
i
=
m
,
s
o
l
v
e
f
o
r
x
Math Input
Natural Language
Math Input