Which of the following statements about the polynomial function f(x)=x^3+2x^2-1

x = -1

x =(1-√5)/-2= 0.618

x =(1+√5)/-2=-1.618

Step  1  :

Equation at the end of step  1  :

 0 -  (((x3) +  2x2) -  1)  = 0  

Step  2  :  

Step  3  :

Pulling out like terms :

3.1     Pull out like factors :

  -x3 - 2x2 + 1  =   -1 • (x3 + 2x2 - 1)  

3.2    Find roots (zeroes) of :       F(x) = x3 + 2x2 - 1

Rational Roots Test is one of the above mentioned tools. It would only find Rational Roots that is numbers  x  which can be expressed as the quotient of two integers

The Rational Root Theorem states that if a polynomial zeroes for a rational number  P/Q   then  P  is a factor of the Trailing Constant and  Q  is a factor of the Leading Coefficient

In this case, the Leading Coefficient is  1  and the Trailing Constant is  -1.

The factor(s) are:

of the Leading Coefficient :  1

of the Trailing Constant :  1

Let us test

 P    Q    P/Q    F(P/Q)    Divisor

     -1       1        -1.00        0.00      x + 1  

     1       1        1.00        2.00      

The Factor Theorem states that if P/Q is root of a polynomial then this polynomial can be divided by q*x-p Note that q and p originate from P/Q reduced to its lowest terms

In our case this means that

  x3 + 2x2 - 1  

can be divided with  x + 1  

Polynomial Long Division :

3.3    Polynomial Long Division

Dividing :  x3 + 2x2 - 1  

                             ("Dividend")

By         :    x + 1    ("Divisor")

dividend     x3  +  2x2      -  1  

- divisor  * x2     x3  +  x2          

remainder         x2      -  1  

- divisor  * x1         x2  +  x      

remainder          -  x  -  1  

- divisor  * -x0          -  x  -  1  

remainder                0

Quotient :  x2+x-1  Remainder:  0  

Trying to factor by splitting the middle term

3.4     Factoring  x2+x-1  

The first term is,  x2  its coefficient is  1 .

The middle term is,  +x  its coefficient is  1 .

The last term, "the constant", is  -1  

Step-1 : Multiply the coefficient of the first term by the constant   1 • -1 = -1  

Step-2 : Find two factors of  -1  whose sum equals the coefficient of the middle term, which is   1 .

     -1    +    1    =    0  

Observation : No two such factors can be found !!

Conclusion : Trinomial can not be factored

Equation at the end of step  3  :

 (-x2 - x + 1) • (x + 1)  = 0  

Step  4  :

Theory - Roots of a product :

4.1    A product of several terms equals zero.  

When a product of two or more terms equals zero, then at least one of the terms must be zero.  

We shall now solve each term = 0 separately  

In other words, we are going to solve as many equations as there are terms in the product  

Any solution of term = 0 solves product = 0 as well.

Parabola, Finding the Vertex :

4.2      Find the Vertex of   y = -x2-x+1

For any parabola,Ax2+Bx+C,the  x -coordinate of the vertex is given by  -B/(2A) . In our case the  x  coordinate is  -0.5000  

Plugging into the parabola formula  -0.5000  for  x  we can calculate the  y -coordinate :  

 y = -1.0 * -0.50 * -0.50 - 1.0 * -0.50 + 1.0

or   y = 1.250

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = -x2-x+1

Axis of Symmetry (dashed)  {x}={-0.50}  

Vertex at  {x,y} = {-0.50, 1.25}  

x -Intercepts (Roots) :

Root 1 at  {x,y} = { 0.62, 0.00}  

Root 2 at  {x,y} = {-1.62, 0.00}  

Solve Quadratic Equation by Completing The Square

4.3     Solving   -x2-x+1 = 0 by Completing The Square .

Multiply both sides of the equation by  (-1)  to obtain positive coefficient for the first term:

x2+x-1 = 0  Add  1  to both side of the equation :

  x2+x = 1

Now the clever bit: Take the coefficient of  x , which is  1 , divide by two, giving  1/2 , and finally square it giving  1/4  

Add  1/4  to both sides of the equation :

 On the right hand side we have :

  1  +  1/4    or,  (1/1)+(1/4)  

 The common denominator of the two fractions is  4   Adding  (4/4)+(1/4)  gives  5/4  

 So adding to both sides we finally get :

  x2+x+(1/4) = 5/4

Adding  1/4  has completed the left hand side into a perfect square :

  x2+x+(1/4)  =

  (x+(1/2)) • (x+(1/2))  =

 (x+(1/2))2

Things which are equal to the same thing are also equal to one another. Since

  x2+x+(1/4) = 5/4 and

  x2+x+(1/4) = (x+(1/2))2

then, according to the law of transitivity,

  (x+(1/2))2 = 5/4

We'll refer to this Equation as  Eq. #4.3.1  

The Square Root Principle says that When two things are equal, their square roots are equal.

Note that the square root of

  (x+(1/2))2   is

  (x+(1/2))2/2 =

 (x+(1/2))1 =

  x+(1/2)

Now, applying the Square Root Principle to  Eq. #4.3.1  we get:

  x+(1/2) = √ 5/4

Subtract  1/2  from both sides to obtain:

  x = -1/2 + √ 5/4

Since a square root has two values, one positive and the other negative

  x2 + x - 1 = 0

  has two solutions:

 x = -1/2 + √ 5/4

  or

 x = -1/2 - √ 5/4

Note that  √ 5/4 can be written as

 √ 5  / √ 4   which is √ 5  / 2

Solve Quadratic Equation using the Quadratic Formula

4.4     Solving    -x2-x+1 = 0 by the Quadratic Formula .

According to the Quadratic Formula,  x  , the solution for   Ax2+Bx+C  = 0  , where  A, B  and  C  are numbers, often called coefficients, is given by :

           - B  ±  √ B2-4AC

 x =   ————————

                     2A

 In our case,  A   =     -1

                     B   =    -1

                     C   =   1

Accordingly,  B2  -  4AC   =

                    1 - (-4) =

                    5

Applying the quadratic formula :

              1 ± √ 5

  x  =    ————

                  -2

 √ 5   , rounded to 4 decimal digits, is   2.2361

So now we are looking at:

          x  =  ( 1 ±  2.236 ) / -2

Two real solutions:

x =(1+√5)/-2=-1.618

or:

x =(1-√5)/-2= 0.618

Solving a Single Variable Equation :

4.5      Solve  :    x+1 = 0  

Subtract  1  from both sides of the equation :  

                     x = -1

Hope this helps.

let's cover over the formula of the vertex:

y = a(x – h)^2 + k

in this formula, (h,k) are the vertex, always remember that the positive or negative value of the vertex is based on the sign it has.

for example, if the vertex is -3,-6 then both the x and y value would have the positive sign attached to it and if it were a positive x and y value, then a negative sign would be attached to it.

with that being said, for our problem the x value is a positive one so we are looking for a number with a negative sign next to it, in this case the first and second choice.

however, for the first answer choice it isn't quite part of the formula so we know that the answer choice correctly displays the x value.

to confirm, we can see if the -1 fits correctly with the second answer choice, and as mentioned above a negative number will have a positive sign attached to it. so, for our problem we can see that -1 has been changed to +1, so we can confirm that the second answer choice is correct.

hence, our final answer is y=(x - 1)^2 + 1