Finding all real zeros

[moronatmath]

I asked how I find all real zeros in an older post but had no reply. Can someone please walk me through this problem? Thank you!

For the function y=x^5 + 3 x^3 - 40 x,

find all real zeros.

The real zeros are x=

 

[tkhunny]

What have you tried?

Absense of the answer to that question may be why you don't get a response.

Can you factor that expression AT ALL? That would be a good place to start.

 

[stapel]

Can someone please walk me through this problem?

Start by taking the common factor out front.

Then notice that what's left in the parentheses is a quadratic in x², and is factorable.

Factor to get (x² - a)(x² - b), and then solve the factors.

Eliz.