C(x) = 3x3 + 450x2
R(x) = 7x3 + 300x2 + 900x
P(x) = R(x) - C(x)
a.) P(x) = 7x3 + 300x2 + 900x - (3x3 + 450x2)
= 7x3 + 300x2 + 900x - 3x3 - 450x2
= 4x3 - 150x2 + 900x
b.) The degree is 3 because that's the highest exponent of the polynomial (profit equation). The leading coefficient is 4. The leading term is 4x3. The constant is zero.
c.) Factor using GCF (greatest common factor).
4x3 - 150x2 + 900x = x(4x2 - 150x + 900) = 2x(2x2 - 75x + 450)
d.) Lets apply the zero product property. Set 2x and 2x2 - 75x + 450 equal to zero.
2x = 0 ⇒ x = 0 or 2x2 - 75x + 450 = 0
Use the quadratic formula to solve for x with a = 2, b = -75, and c = 450.
x = (-b ± √b2 - 4ac) / 2a = [-(-75) ± √752 - 4(2)(450)] / 2(2)
= (75 ± √5625 - 3600) / 4
= (75 ± √2025) / 4
= (75 ± 45) / 4
x = (75 + 45) / 4 = 120 / 4 = 30 or x = (75 - 45) / 4 = 30 / 4 = 7.5
The solutions are x = 0, 7.5, and 30. The company will break even at the initial start (0 months), 7.5 months, and 30 months (2.5 years).