Question 377873
I am trying to find out the slope intercept form of the equation of the line passing through these points (8,-6), (4,-2).  I am using the formula y=mx+b. 
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Slope m = diffy/diffx = (4/-4) = -1
Use y = mx + b and either point to find b
-6 = -1*8 + b
b = 2
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y = -x + 2
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The other tutor used diffx/diffy.  That might give the correct answer for this one, but it's not correct in general.