Evaluate the polynomial for x=3 and x=-3

Question

-3x^3+8x^2-5x-9

Answer 1

Hello, Ruby

Just plug in the values of x into the expression.  Ok. Let's get stated. For x= 3.

 

-3x^3      + 8 x^2    -5x     -9       Substituting x for 3.

-3(3)^3   + 8(3)^2   -5(3)  -9       Evaluating the exponents

-3(27)     + 8(9)        -5(3)  -9       Multiplying 

-81           + 72         -15     -9       Add/subtract from left to right

                 -9-15-9 

                      -33

So, when x=3, the value of the expression is 33. Proceeding to the second half, we have the same expression.  

 

-3(-3)^3        + 8(-3)^2  -5( -3)  -9       Evaluating the exponents

-3(-27)          + 8(9)        + 15    -9        Multiplying

   81              + 72           + 15    -9        Add/subtract 

                            159 

 

I hope this helps out and thanks for posting.

D.Y. T.

dont forget to rate me:)

Answer 2

f(3)=-33

f(-3)=159