SOLUTION: When -3x^3 - 4 is divided by x + 2 , what is the remainder?

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Question 1153219: When -3x^3 - 4 is divided by x + 2 , what is the remainder?
Found 3 solutions by MathLover1, Theo, ikleyn:
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!
is divided by

...........(
|
..............
...................
...................
.......................
.......................
........................... => remainder

Answer by Theo(13342)   (Show Source): You can put this solution on YOUR website!
the remainder is 20.
you can use synthetic division or polynomial division.
here's a reference on polynomial division.
https://www.mathsisfun.com/algebra/polynomials-division-long.html
here's a refeence on synthetic division.
https://mathbitsnotebook.com/Algebra2/Polynomials/POPolySynDivide.html
here's my worksheet.
$$$

Answer by ikleyn(52810)   (Show Source): You can put this solution on YOUR website!
.

There is MUCH SIMPLER WAY to get the answer.


Notice, that the remainder of dividing the given polynomial by binomial (x+2) is a constant term.


Use the Remainder theorem:  the remainder of division of any polynomial f(x) by a binomial (x-a) is equal 
to the value f(a) of the polynomial at x= a:


In your case, the remainder of division of the given polynomial  f(x) = -3x^3-4  by (x+2) is equal to


    f(-2) = -3*(-2)^3-4 = -3*(-8)-4 = 24-4 = 20.    ANSWER

Solved.

By using this method, you do not need to perform division (!)

------------------

   Theorem   (the remainder theorem)
   1. The remainder of division the polynomial    by the binomial    is equal to the value    of the polynomial.
   2. The binomial    divides the polynomial    if and only if the value of    is the root of the polynomial  ,  i.e.  .
   3. The binomial    factors the polynomial    if and only if the value of    is the root of the polynomial  ,  i.e.  .


See the lessons
    - Divisibility of polynomial f(x) by binomial x-a and the Remainder theorem
    - Solved problems on the Remainder thoerem
in this site.


Also,  you have this free of charge online textbook in ALGEBRA-II in this site
    ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic
"Divisibility of polynomial f(x) by binomial (x-a). The Remainder theorem".

Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.



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