Answer:
Step-by-step explanation: what triangle?
Concave up is U-shaped.
There will be a inflection/critical point f'(x) =0 then a negative slope f'(x) = neg then another inflection/critical point f'(x) =0 at the bottom of the U-shape then a positive slope to last inflection/critical point. The interval for the Concave Up shape is the first and last inflection points.
Number of nickels plus number of dimes equals total number of coins
so
n + d = 40
then they tell us that "there are seven times as many dimes as there are nickels"
this translates to
d = 7n
we then plug that into our first equation
and get
n + 7n = 40
then we solve for n
add like terms
8n = 40
then divide both sides by 8
n = 40/8 = 5
therefore Jimmy has 5 nickels
