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18. Simplify [tex]\left(15 x^2 - 24 x + 9\right) \div (3 x - 3)[/tex]:

A. [tex]5x + 3[/tex]

B. [tex]5x - 13[/tex] with a -30 remainder

C. [tex]5x + 13[/tex] with a -30 remainder

D. [tex]5x - 3[/tex]


Sagot :

To simplify [tex]\(\left(15 x^2 - 24 x + 9\right) \div (3 x - 3)\)[/tex], we need to perform polynomial division.

### Step-by-Step Solution

1. Set up the division: We are dividing the polynomial [tex]\(15 x^2 - 24 x + 9\)[/tex] by [tex]\(3 x - 3\)[/tex].

2. Divide the leading terms:
- The leading term of the numerator is [tex]\(15 x^2\)[/tex].
- The leading term of the denominator is [tex]\(3 x\)[/tex].
- Divide [tex]\(15 x^2\)[/tex] by [tex]\(3 x\)[/tex]: [tex]\(\frac{15 x^2}{3 x} = 5 x\)[/tex].

This tells us that the leading term of the quotient is [tex]\(5 x\)[/tex].

3. Multiply the entire denominator by this term:
- Multiply [tex]\(3 x - 3\)[/tex] by [tex]\(5 x\)[/tex]:
[tex]\[ (3 x)(5 x) + (-3)(5 x) = 15 x^2 - 15 x \][/tex]

4. Subtract this result from the original numerator:
[tex]\[ (15 x^2 - 24 x + 9) - (15 x^2 - 15 x) = (-24 x + 15 x) + 9 = -9 x + 9 \][/tex]

5. Repeat the process with the new polynomial:
- Divide the leading term of the new polynomial [tex]\(-9 x\)[/tex] by the leading term of the denominator [tex]\(3 x\)[/tex]:
[tex]\[ \frac{-9 x}{3 x} = -3 \][/tex]

This tells us that the next term of the quotient is [tex]\(-3\)[/tex].

6. Multiply the entire denominator by this new term:
- Multiply [tex]\(3 x - 3\)[/tex] by [tex]\(-3\)[/tex]:
[tex]\[ (3 x)(-3) + (-3)(-3) = -9 x + 9 \][/tex]

7. Subtract this result from the current polynomial:
[tex]\[ (-9 x + 9) - (-9 x + 9) = 0 \][/tex]

Since the remainder is zero, the division is exact.

### Final Result

The quotient of the division is:
[tex]\[ 5 x - 3 \][/tex]

The simplified form of [tex]\(\left(15 x^2 - 24 x + 9\right) \div (3 x - 3)\)[/tex] is therefore:

[tex]\[ 5 x - 3 \][/tex]

So the correct answer is:
D. [tex]\(5 x - 3\)[/tex]