help with some relevant maths for perf calcs

[compressor stall]

thanks for the reply - a bit more info
Calcs based n the following data (col\'s 1 and 2) straight from the manual. (sorry about the layout - does not like tabs in cut 'n paste!)

Column 1: Flight level
Column 2: FF at 5000kg using flight man. '
Column 3: FF at 5000kg using equation

0 356 356
10 346 346
20 336 337
30 328 329
40 320 320
50 312 312
60 304 304
70 297 296
80 290 289
90 283 281
100 275 275
110 268 268
120 261 261
130 255 255
140 249 249
150 244 244
160 238 238
170 234 233
180 228 228
190 224 224
200 219 220
210 215 215
220 211 212

Using the tables in the book, I plottted in excel column one against column two and created a trendline that gave a formula [fflow(wt) = 0.0118x^2 - 0.3454x + 343.43] that gave the results in column 3. These results are well within the tolerence I expected.

Same process to with following data to get the second eq: fflow(alt) = 0.0012a^2 - 0.9261a + 355.21..

wt(/100kg) ff@SL
50 356
55 360
60 365
65 371
70 377
75 384
80 391
81 393

Now I wish to find link the two => input alt and weight and get a fflow.

EDIT---should read 5000kg atop the first lot of data! sorry.