2 factors of x3 + px2 + qx + r are: (x + a) and (x + b)

[Gehan]

Hi everyone, new to the forum. I do not know how to solve this question ( year 10):

Two of the factors of x3 + px2 + qx + r are: (x + a) and (x + b). Find the third factor

The answer I got from the book is: (x − p + (a + b)), but I do not know how!!!!!

Can you please help me :roll:

Thank you

 

[Deleted member 4993]

Hi everyone, new to the forum. I do not know how to solve this question ( year 10):

Two of the factors of x3 + px2 + qx + r are: (x + a) and (x + b). Find the third factor

The answer I got from the book is: (x − p + (a + b)), but I do not know how!!!!!

Can you please help me :roll:

Thank you

Assume the other factor is 'x - c'

Then:

x³ + px² + qx + r = (x + a)(x + b)(x - c)

Now equate the coefficients of x³, x² and x.

What are your thoughts?

Please share your work with us ...even if you know it is wrong

If you are stuck at the beginning tell us and we'll start with the definitions.

You need to read the rules of this forum. Please read the post titled "Read before Posting" at the following URL:

http://www.freemathhelp.com/forum/th...Before-Posting