05/26/2025
ππ At first glance, we see perfect squares. This will make todayβs exercise marginally easier. In step 1, βx - 1β is found to be a factor after some trial-and-error. Trial-and-error meaning substitute β1β for βxβ in f(x) and verify whether or not f(x = 1) = 0. If true, βx - 1β is a factor of the given polynomial. If false, βx - 1β is not a factor. Proceed by testing 2, then 3, then 4, and so on. (The same can be done with negative numbers).
Next, we separate βx - 1β into two βgroupsβ with each group being multiplied by a distinct coefficient. The sum of these coefficients is in fact the quotient of β4(x^3) - 4(x^2) - 25x + 25β divided by βx - 1.β Further factorization of the said quotient, gives us two additional factors: β2x + 5β and β2x - 5.β Solving each of the three factors results in the x-values shown in step 1.
Step 2 illustrates a derivation, fβ(x), and domains where f(x) increases and decreases.
Step 3 covers an additional derivation, fβ(x), and domains where f(x) βopens upβ and βopens down.β