The answer is supposed to be -2(e^x - e^-x)/(e^x + e^-x)^2 but i’m not sure how to get there because my answer always ends up as -2(e^x + e^-x)/(e^x+e^x)^2, so i’m not sure where i’m missing the negative or if the answer key has a typo.

The answer to your question is below

Step-by-step explanation:

Derivative of a quotient  

f'(x) = 0

g'(x) =

g²(x) = (

Substitution

Simplification and result

if gloria has "carry over" minutes, (that is, any minutes paid for but not used in a month can be applied to her payment for minutes in the next month,) her total usage for the three months is: total minutes = 320 + 243 + 489 = 1052 minutes number of 200 minute blocks = 1052/200 = 5 r52 (that is 5 with a remainder of 52) rounding up the number of 200 minute blocks gives her usage for the three months as 6 blocks. the cost for six blocks is 6 x $25 = $150 she also has 200 - 52 or 148 carry over minutes if gloria pays each month and unused minutes are lost, applying the rounding up procedure to each month gives: first month usage of 320 minutes rounds up to 2 blocks of 200 minutes for a payment of 2 x $25 = $50 second month usage of 243 minutes rounds up to 2 blocks of 200 minutes for a payment of 2 x $25 = $50 third month usage of 489 minutes rounds up to 3 blocks of 200 minutes for a payment of 3 x $25 = $75 total payments for the three months are $50 + $50 + $75 = $175 get the plan with carry over minutes!