If x(b)= 20-15b+2b^2 then why would average and instantaneous velocity values be the same? If x(b)= 20-15b+2b^3 then why would average and instantaneous velocity values be different? What would the magnitude of the difference mean? I think in x(b)= 20-15b+2b^2 average and instantaneous velocity values are the same because the formula for average velocity calculates the slope of two b centered at the b between the two different b. While the formula for instantaneous velocity is the line for the slope of t, which is also the center of two different t. But then it wouldn't make sense for x(b)= 20-15b+2b^3. Basically I don't have any idea for the second equation. Thank you for your help!