scatter chart problem

[#1]

The 1st picture is my scatter chart and the 2nd is wat the result i need. so i want to ask hw can i add the line into my scatter chart? the line mayb depand on average or correralation line also can.

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[#2]

Goto the presentation tab, add reference lines.

[#3]

jz simply go to the presentation tab and add a reference lines only? need any setting? i'm a newbie of QV, please hlp me. Thank~

[#4]

this is wat after i added the trendlines. May i ask what is the trendlines stand for?

[#5]

trendlines are usually used to show an average and you could see how your values fare against the average.

[#6]

for my job i need to add 1 line which is like the trendlines but i need to used my own formula so that the line can do the calculation based on my formula. i want to ask QV is able to do this job or not?