SOLUTION: Hi - last one for the assignment! I am doing well in this class, but this chapter truly has me stumped! Problem: -3x^3+4x^2-x-2 for x = -2 Again - I can't thank you folks

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Hi - last one for the assignment! I am doing well in this class, but this chapter truly has me stumped! Problem: -3x^3+4x^2-x-2 for x = -2 Again - I can't thank you folks      Log On


   



Question 248447: Hi - last one for the assignment!
I am doing well in this class, but this chapter truly has me stumped!
Problem:
-3x^3+4x^2-x-2 for x = -2
Again - I can't thank you folks enough!

Found 2 solutions by richwmiller, jsmallt9:
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
Not sure what the problem is.
I assume you are plugging -2 in for x
-3x^3+4x^2-x-2 for x = -2
-3(-2)^3+4(-2)^2-(-2)-2
-3(-8)+4(4)+2-2
24+16+2-2
=40

Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
I assume the problem is to evaluate
-3x%5E3%2B4x%5E2-x-2 for x = -2

There are two ways to do this:
  • Use Synthetic Division:
    -2 |  -3  4  -1  -2
    ----      6 -20  42
          --------------
          -3 10 -21  40
    

    The expression has a value of 40 (the remainder above) when x = -2. (If you don;t know why, look up the Remainder Theorem.)
  • Straightforward. Just substitute -2 into the expression for x:
    -3%28-2%29%5E3+%2B+4%28-2%29%5E2+-+%28-2%29+-+2
    and simplify:
    -3%28-8%29+%2B+4%284%29+%2B+2+-+2
    24+%2B+16+%2B+2+-+2
    40