Answer:
f(x)=(x-2)(x+2)(x-5)
Step-by-step explanation:
f(x)=x³-5x²+4x-20 1. Just group randomly
f(x)=x²(x-5)+4(x-5) 2. Factor the groupings
f(x)=(x²+4)(x-5)
<u>f(x)=(x-2)(x+2)(x-5)</u> 3. Factor the difference of two squares
Let's say hmm let's use the figures in thousands, so
model A costs 90 + 4 per year, so... ok.. after "t" years, then the cost for model A is then 90 + 4*t, or
A = 90 + 4t.
now, model B is 70 + 10 per year, so,... after "t" years, model B is then
B = 70 + 10 * t, or
B = 70 + 10t.
if we were to assume A < B, namely the cost of A is less than B, what would the years be? namely, what's "t"?

after that period, then A becomes cheaper than B.
Answer:
20
Step-by-step explanation:
Sn = (n/2)(a1 + a1 + d(n-1)), where S = sum, a1 = first term, n = number of terms, d = common difference
400 = (n/2)(1 + 1 + 2(n - 1))
400 = (n/2)(2 + 2n - 2)
400 = (n/2)(2n
400 = n2
20 = n
Twenty numbers are in the set.