Math  /  Algebra

QuestionUse synthetic division to determine if the given value for kk is a zero of this polynomial. If not, determine p(k)p(k). p(x)=4x419x39x2+98x24;k=3p(x)=4 x^{4}-19 x^{3}-9 x^{2}+98 x-24 ; k=3

Studdy Solution

STEP 1

What is this asking? Is 33 a root of the polynomial 4x419x39x2+98x244x^4 - 19x^3 - 9x^2 + 98x - 24?
If not, what's the polynomial's value at x=3x = 3? Watch out! Remember, a value kk is a zero of a polynomial if the remainder after synthetic division by xkx-k is **zero**!
Don't mix up the remainder with the result.

STEP 2

1. Set up the synthetic division
2. Perform the synthetic division
3. Interpret the result

STEP 3

Alright, let's **set up** our synthetic division!
We'll put our **potential root**, k=3k = 3, outside the box.
Inside, we'll list the coefficients of our polynomial p(x)=4x419x39x2+98x24p(x) = 4x^4 - 19x^3 - 9x^2 + 98x - 24, which are 44, 19-19, 9-9, 9898, and 24-24.

STEP 4

So, it looks like this:
341999824\begin{array}{cccccc} 3 & 4 & -19 & -9 & 98 & -24 \\ \end{array}

STEP 5

Bring down the **leading coefficient**, 44, below the line.
3419998244\begin{array}{cccccc} 3 & 4 & -19 & -9 & 98 & -24 \\ & 4 & & & & \end{array}

STEP 6

**Multiply** 33 by 44 to get 34=123 \cdot 4 = 12, and place it under the next coefficient, 19-19.
341999824412\begin{array}{ccccc} 3 & 4 & -19 & -9 & 98 & -24 \\ 4 & 12 \end{array}

STEP 7

**Add** 19-19 and 1212 to get 19+12=7-19 + 12 = -7, and write the result below the line.
34199982447\begin{array}{cccccc} 3 & 4 & -19 & -9 & 98 & -24 \\ 4 & -7 \end{array}

STEP 8

**Repeat** this process: multiply 33 by 7-7 to get 21-21, add it to 9-9 to get 30-30, multiply by 33 to get 90-90, add it to 9898 to get 88, multiply by 33 to get 2424, and finally, add it to 24-24 to get 00.
341999824473080\begin{array}{cccccc} 3 & 4 & -19 & -9 & 98 & -24 \\ 4 & -7 & -30 & 8 & 0 \end{array}

STEP 9

That **last number**, 00, is our **remainder**!
Since the remainder is 00, we know that k=3k = 3 *is* a zero of the polynomial!
Woohoo!

STEP 10

33 is a zero of the polynomial p(x)=4x419x39x2+98x24p(x) = 4x^4 - 19x^3 - 9x^2 + 98x - 24, as the remainder after synthetic division is 00.

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