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) About Me  (Show Source):
You can put this solution on YOUR website!
-3x%5E3+-+4 is divided by x+%2B+2

...........(-3x%5E2%2B6x-12
x+%2B+2|-3x%5E3%2B0%2Ax%5E2%2B0%2Ax+-+4
..............-3x%5E3-6x%5E2
...................6x%5E2
...................6x%5E2%2B12x
.......................-12x
.......................-12x-24
........................... 20=> remainder
-3+x%5E3+-+4+=+%28-3x%5E2+%2B+6+x+-+12%29+%2A+%28x+%2B+2%29+%2B+20

Answer by Theo(13342) About Me  (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) About Me  (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 (!)

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   Theorem   (the remainder theorem)
   1. The remainder of division the polynomial  f%28x%29  by the binomial  x-a  is equal to the value  f%28a%29  of the polynomial.
   2. The binomial  x-a  divides the polynomial  f%28x%29  if and only if the value of  a  is the root of the polynomial  f%28x%29,  i.e.  f%28a%29+=+0.
   3. The binomial  x-a  factors the polynomial  f%28x%29  if and only if the value of  a  is the root of the polynomial  f%28x%29,  i.e.  f%28a%29+=+0.


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.