QUIZ: Synthetic and Polynomial Long Division

What is the result of dividing [tex]$x^3-6[tex]$[/tex] by [tex]$[/tex]x+2$[/tex]?

A. [tex]$x^2 - 2x + 4 + \frac{14}{x+2}$[/tex]

B. [tex]$x^2 - 2x + 4 - \frac{14}{x+2}$[/tex]



Answer :

To divide \(x^3 - 6\) by \(x + 2\), we use polynomial division. Here is the step-by-step process:

1. Set up the division:
[tex]\[ \frac{x^3 + 0x^2 + 0x - 6}{x + 2} \][/tex]
This expression means we are dividing \(x^3 + 0x^2 + 0x - 6\) by \(x + 2\).

2. First term:
To find the first term of the quotient, divide the leading term of the dividend (\(x^3\)) by the leading term of the divisor (\(x\)):
[tex]\[ \frac{x^3}{x} = x^2 \][/tex]
Multiply \(x^2\) by the entire divisor (\(x + 2\)):
[tex]\[ x^2 \cdot (x + 2) = x^3 + 2x^2 \][/tex]
Subtract this product from the original dividend:
[tex]\[ (x^3 + 0x^2 + 0x - 6) - (x^3 + 2x^2) = -2x^2 + 0x - 6 \][/tex]

3. Second term:
Now, divide the leading term of the new polynomial (\(-2x^2\)) by the leading term of the divisor (\(x\)):
[tex]\[ \frac{-2x^2}{x} = -2x \][/tex]
Multiply \(-2x\) by \(x + 2\):
[tex]\[ -2x \cdot (x + 2) = -2x^2 - 4x \][/tex]
Subtract this product from the new polynomial:
[tex]\[ (-2x^2 + 0x - 6) - (-2x^2 - 4x) = 4x - 6 \][/tex]

4. Third term:
Next, divide the leading term of the new polynomial (\(4x\)) by the leading term of the divisor (\(x\)):
[tex]\[ \frac{4x}{x} = 4 \][/tex]
Multiply \(4\) by \(x + 2\):
[tex]\[ 4 \cdot (x + 2) = 4x + 8 \][/tex]
Subtract this product from the new polynomial:
[tex]\[ (4x - 6) - (4x + 8) = -14 \][/tex]

Thus, the quotient of the division is \(x^2 - 2x + 4\) and the remainder is \(-14\).

Putting everything together, we get:
[tex]\[ \frac{x^3 - 6}{x + 2} = x^2 - 2x + 4 + \frac{-14}{x + 2} \][/tex]

Simplifying the expression gives us:
[tex]\[ x^2 - 2x + 4 - \frac{14}{x + 2} \][/tex]

Therefore, the answer is:
[tex]\[ x^2 - 2x + 4 - \frac{14}{x + 2} \][/tex]