For y = x^4 - 72x^2 - 17, how would i find each of these? a) where the function is increasing b) where the function is decreasing c) where the function is concave up d) where the function is concave down e) inflection points

For the answer to the question above,
a) dy/dx = 4x^3 - 144x. When is this > 0? When x^3 > 36x. 
b) When is dy/dx < 0? When x^3 < 36x 
c) 2nd derivative = 12x^2 - 144. Concave up when 2nd derivative is positive 
d) Concave down when 2nd derivative is negative 
e) dy/dx = 0 when x = 0, -6, +6 
f ) 2nd derivative = 0 when 12x^2 - 144 = 0, x = -sqrt(12) and +sqrt(12)

The answer is c because you turn 17.5% into a decimal which gives you .175 then you times that by $361.35 which gives you 63.23625 but then you round that which gives you 63.24. then you at 63.24 pulse 361.35 and you round it which gives you $425

The answer would be the second choice : )