Linear trendline is giving wrong equation and starting below 0. HELP PLEASE

Hi, I have done a simple scattergraph and I need to insert a trendline to get the equation so I can find more values.
I insert a trendline and it changes my y axis scale and starts below 0. I don't want this to happen
I also click on show equation and it gives me something like Y = 0.123 - 0.321 I should be getting an equation that is y = mx+c......not - c.
I knew this equation was wrong but I manually substituted the y and x with known values to double check the equation was correct but it gives an answer nowhere near the correct answer.
I'm not very knowledgable when it comes to excel so please try explain in simple terms
I would be so grateful if anyone could help thank you!!!!

Can you post a workbook containing your graph please...

click go advanced and then manage attachments.

image.jpg


Hope you can see that well enough

I don't think this is a problem with excel, that looks ok to me...

in the equation
y=mx+c

c represents where the line crosses the y axis.

If you draw a best fit line through your data, it is clear it would cross the y axis below 0, therefore c is a negative number.
Using the equation on the graph, the numbers seem to tie up well.
for example
1.284*(2.1)-1.62 = 1.077, compared to 1.158

If you want your best fit line to go from 0, then change it from linear to a power.

Just realised where I've been going wrong. You are very right, thanks for explaining it in simple terms for me! Much appreciated