Step-by-step explanation: K subtracted by 8.4 is greater than 21, so we start the equality off with our unknown variable K. Because K-8.4 is greater than 21, our symbol faces the direction of K-8.4 (symbol always faces the direction of the greater values).
A 4th degree polynomial will have at most 3 extreme values. Since the degree is even, there will be one global extreme, with possible multiplicity. The remainder, if any, will be local extremes that may be coincident with each other and/or the global extreme.
(The number of extremes corresponds to the degree of the derivative, which is 1 less than the degree of the polynomial.)
A rational number is a number able to be put into a fraction, an irrational number is not able to be. Therefore, when adding the two, the rational and the irrational will be irrational. For example, 2 is a rational number, and 1.8903 is irrational. If you add the two, you will get 3.18903, which is unable to be put into a fraction.