Question 390372
13 - 51
15 - 49
22 - 42
33 - 31
36 - 28 
Input / output .. I need the Rule here thanks 
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The relation is linear.
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Use two of the pairs to find the slope:
m = (49-51)/(15-13) = -1
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Form: y = mx + b
Substitute for y,x and m, then solve for "b":
51 = -1(13)+b
b = 64
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Equation:
y = -x+64
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Cheers,
stan H.