Answer:

Step-by-step explanation:
<u>Use identities to set the equation up as a quadratic</u>

<u>Make the substitution u=cos(x) and solve the quadratic</u>
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Hence, 
Answer:
Part A:
P(x)=15x^4+30x^3-50
Part B:
P(4)=$4270
Step-by-step explanation:
Part A:
In order to find the profit function P(x) we have to integrate the P'(x)
P'(x)=x(60x^2+90x)
P'(x)=60x^3+90x^2

P(x)=15x^4+30x^3+C
when x=0, C=-50
P(x)=15x^4+30x^3-50
Part B:
x=4
P(x)=15x^4+30x^3-50
P(4)=15*4^4+30*4^3-50
P(4)=$4270
Profit from selling 400 pounds is $4270
I think its 1.25ft but i could be wrong... sorry if im wrong
It should be the answers if not sorry
Answer:
A) X<1
B) X>7
C)X<6
D)X>-3