222k views
3 votes
Please help me answer this question. Show steps and explain

Describe the graph of the function f(x)=x^3+2x^2-5x-6.
Include the x and y-intercept, and end behaviors. Show work.
Factors of p/q_____________
Test the factors______________
x-intercepts_____________
y-intercepts__________________
end behaviors_____________________

1 Answer

3 votes

Your problem statement makes no reference to p or q, so we can only guess that "p/q" refers to the ratio of the lowest- and highest-degree coefficients:

... -6/1

Then the factors of p/q are the factors of 6, with either sign.

Factors of p/q: ±1, ±2, ±3.

There are a number of ways the factors can be tested. To test 1, simply add the coefficients. (The sum is -8.) To test -1, subtract the sum of odd-degree coefficients from the sum of even-degree coefficients. (The difference is 0.)

Knowing that -1 is a root of the function, you can use synthetic division to find the quadratic factor. (See the first attachment for the work.) Then you have ...

... f(x) = (x +1)(x² +x -6)

You can continue to test the factors of p/q, or you can factor the quadratic to get ...

... f(x) = (x +1)(x -2)(x +3)

Another way to test the factors is to program your graphing calculator to evaluate the function f(x) for those factors. The result from my TI-84 is shown in the second attachment. That shows f(x) = 0 for x = -3, -1, and +2.

Test the factors: f({-3, -2, -1, 1, 2, 3}) = {0, 4, 0, -8, 0, 24}

This tells you the x-intercepts.

X-intercepts: -3, -1, 2

Of course, the y-intercept is just the constant in the function—the value of the function when x=0.

Y-intercept: -6

As with any odd-degree polynomial with a positive leading coefficient, the overall behavior looks like "/". That is ...

End behaviors: f(x) goes to -∞ as x goes to -∞; f(x) goes to +∞ as x goes to +∞.

_____

A graph of f(x) is shown in the third attachment. (Graphing calculators make it easy to use graphing to find x-intercepts.)

Please help me answer this question. Show steps and explain Describe the graph of-example-1
Please help me answer this question. Show steps and explain Describe the graph of-example-2
Please help me answer this question. Show steps and explain Describe the graph of-example-3
User Kanwaljeet Singh
by
8.8k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories