Asked by ANDREW

HI

linear equation help please...

I have plotted known numbers into an excel spreadsheet and it shows the formula as:


I am struggling to find the answer to x..??

could you go through it step by step please.....am trying to find ppm of a concentration of iron in test sample....

Concentration (ppm=mg/L) were 0 1 2 3 and 5
absorbance was 0 0.190 0.411 0.590 0.975

I graphed these in excel and these results came up y=0.1954x +0.0033

the example given at school had y=0.1954x +0.0033 (r squared =0.9993) and they came up with 2.08 ppm ......

I fail to get how they got that answer...:)

Thanks so much in advance..:)
Answered by scott
it seems that you generated an equation for finding ppm if you know the absorbance

in the school example, there must have been an absorbance for an unknown ppm

you seem to be missing a piece of data
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