The polynomial equation p(x)=x^4-4x^3-4x^2+20x-5 does not have any rational roots. However, it does have four irrational roots. Use your calculator to find 3 decimal place (rounded) approximations for these roots. --- (i am not sure how to do this on my calculator)

Question

The polynomial equation p(x)=x^4-4x^3-4x^2+20x-5 does not have any rational roots. However, it does have four irrational roots. Use your calculator to find 3 decimal place (rounded) approximations for these roots. ---> (i am not sure how to do this on my calculator)

asnaseer · Answer

The only thing I can think of here is that they must assume that you have a graphing calculator. If you do then just plot this polynomial and the roots will be where it crosses the x-axes

aum · Answer

If you do not have access to a graphing calculator, try online sites such as: https://www.desmos.com/calculator Plot the graph and find the x-intercepts. Those are the roots.

aum · Answer

http://gyazo.com/24bfea77eaaead0334447742438fd442

anonymous · Answer

http://www.wolframalpha.com/input/?i=x^4-4x^3-4x^2%2B20x-5

aum · Answer

If you are not allowed to use the graphing calculator let us know.  We can find by trial and error between what two numbers the polynomial changes sign and keep refining the results until it is accurate to 3 decimal places.  But it will take a while to find all 4 roots.

aem9296 · Answer

@aum sorry i responded so late. I have a calculator and we are aloud to use it. Im just not sure on how it works haha

aum · Answer

Online calculator can be used as shown above.

But you can go through some examples in your calculator manual to find out how to graph f(x) and find its roots.

aem9296 · Answer

thank you i got it! @aum

aum · Answer

you are welcome.