Respuesta :
We will investigate how to determine the end behaviours of polynomial functions.
The function given to us is:
[tex]f(x)=123x^3+9x^4-786x-3x^{5^{}}-189x^2\text{ + 1260}[/tex]Whenever we try to determine the end-behaviour of any function. We are usually looking for value of f ( x ) for the following two cases:
[tex]x\to\infty\text{ and x}\to-\infty[/tex]The most important thing to note when dealing with end-behaviour of polynomial functions is that the behaviour is pre-dominantly governed by the highest order term of a polynomial. The rest of the terms are considered small or negligible when considering end-behaviours of polynomials.
The highest order terms in the given function can be written as:
[tex]f(x)=-3x^5[/tex]Then the next step is to consider each case for the value of ( x ) and evaluate the value of f ( x ) respectively.
[tex]\begin{gathered} x\to\infty \\ f\text{ ( }\infty\text{ ) = -3}\cdot(\infty)^5 \\ f\text{ ( }\infty\text{ ) = -3}\cdot\infty \\ f\text{ ( }\infty\text{ ) = -}\infty \end{gathered}[/tex]Similarly repeat the process for the second case:
[tex]\begin{gathered} x\to-\infty \\ f\text{ ( -}\infty\text{ ) = -3}\cdot(-\infty)^5 \\ f\text{ ( -}\infty\text{ ) = 3}\cdot\infty \\ f\text{ ( -}\infty\text{ ) = }\infty \end{gathered}[/tex]Combining the result of two cases we get the following solution:
[tex]As\text{ x}\to\text{ }\infty\text{ , y}\to\text{ -}\infty\text{ and as x}\to-\infty\text{ , y}\to\text{ }\infty[/tex]Correct option is:
[tex]\text{Option C}[/tex]