given f(x) = 4x+8 and g(x) = x^2+x; find (f • g)(-5)
First, we need to find the value of g(-5) by plugging -5 into the function g(x) = x^2 + x:
g(-5) = (-5)^2 + (-5) = 25 - 5 = 20
Now, we need to find (f • g)(-5) by multiplying f(x) and g(x) and then plugging -5 into the resulting function:
f • g = (4x + 8)(x^2 + x)
= 4x^3 + 4x^2 + 8x + 8x
= 4x^3 + 4x^2 + 16x
Therefore,
(f • g)(-5) = 4(-5)^3 + 4(-5)^2 + 16(-5)
= 4(-125) + 4(25) - 80
= -500 + 100 - 80
= -480
So, (f • g)(-5) = -480.