Thanks for your reply,
I tried to use the example, but still not working.
a: =INDEX(LINEST($B$2:$B$6;$A$2:$A$6^{1,2});1;1)
b: =INDEX(LINEST($B$2:$B$6;$A$2:$A$6^{1,2});1;2)
c: =INDEX(LINEST($B$2:$B$6;$A$2:$A$6^{1,2});1;3)
[TABLE="width: 96"]
<tbody>[TR]
[TD="class: xl65, width: 64"]X[/TD]
[TD="class: xl65, width: 64"]Y[/TD]
[/TR]
[TR]
[TD="class: xl66, width: 64"]5[/TD]
[TD="class: xl66, width: 64"]38[/TD]
[/TR]
[TR]
[TD="class: xl66, width: 64"]10[/TD]
[TD="class: xl66, width: 64"]123[/TD]
[/TR]
[TR]
[TD="class: xl66, width: 64"]15[/TD]
[TD="class: xl66, width: 64"]258[/TD]
[/TR]
[TR]
[TD="class: xl66, width: 64"]20[/TD]
[TD="class: xl66, width: 64"]443[/TD]
[/TR]
[TR]
[TD="class: xl66, width: 64"]25[/TD]
[TD="class: xl66, width: 64"]678[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]a[/TD]
[TD="align: right"]15,78921[/TD]
[/TR]
[TR]
[TD]b[/TD]
[TD="align: right"]-110,514[/TD]
[/TR]
[TR]
[TD]c[/TD]
[TD="align: center"]#REF![/TD]
[/TR]
</tbody>[/TABLE]