Question 6 (5 points)

Find [tex]\((f \cdot g)(x)\)[/tex] and [tex]\((f \div g)(x)\)[/tex] for [tex]\(f(x)=15x^2+19x+6\)[/tex] and [tex]\(g(x)=5x+3\)[/tex].

A. [tex]\((f \cdot g)(x) = 3x + 2\)[/tex] and [tex]\((f \div g)(x) = 75x^3 + 57x^2 + 18x + 18\)[/tex]
B. [tex]\((f \cdot g)(x) = 75x^3 + 140x^2 + 87x + 18\)[/tex] and [tex]\((f \div g)(x) = 3x + 2\)[/tex]
C. [tex]\((f \cdot g)(x) = 75x^3 + 57x^2 + 18x + 18\)[/tex] and [tex]\((f \div g)(x) = 3x + 2\)[/tex]
D. [tex]\((f \cdot g)(x) = 3x + 2\)[/tex] and [tex]\((f \div g)(x) = 75x^3 + 140x^2 + 87x + 18\)[/tex]



Answer :

To solve the problem of finding [tex]\((f \cdot g)(x)\)[/tex] and [tex]\((f \div g)(x)\)[/tex] for the given functions [tex]\(f(x) = 15x^2 + 19x + 6\)[/tex] and [tex]\(g(x) = 5x + 3\)[/tex], let's go through the process step-by-step.

### Multiplying the Polynomials

To find [tex]\((f \cdot g)(x)\)[/tex], we multiply the two polynomials:

[tex]\[ f(x) = 15x^2 + 19x + 6 \][/tex]
[tex]\[ g(x) = 5x + 3 \][/tex]

We distribute each term in [tex]\(g(x)\)[/tex] across the polynomial [tex]\(f(x)\)[/tex]:

[tex]\[ (15x^2 + 19x + 6) \cdot (5x + 3) \][/tex]

First, distribute [tex]\(5x\)[/tex] across each term in [tex]\(f(x)\)[/tex]:

[tex]\[ 5x \cdot 15x^2 = 75x^3 \][/tex]
[tex]\[ 5x \cdot 19x = 95x^2 \][/tex]
[tex]\[ 5x \cdot 6 = 30x \][/tex]

Next, distribute [tex]\(3\)[/tex] across each term in [tex]\(f(x)\)[/tex]:

[tex]\[ 3 \cdot 15x^2 = 45x^2 \][/tex]
[tex]\[ 3 \cdot 19x = 57x \][/tex]
[tex]\[ 3 \cdot 6 = 18 \][/tex]

Now, add all these products together:

[tex]\[ 75x^3 + 95x^2 + 30x + 45x^2 + 57x + 18 \][/tex]

Combine like terms:

[tex]\[ 75x^3 + (95x^2 + 45x^2) + (30x + 57x) + 18 \][/tex]
[tex]\[ 75x^3 + 140x^2 + 87x + 18 \][/tex]

Thus, [tex]\((f \cdot g)(x) = 75x^3 + 140x^2 + 87x + 18\)[/tex].

### Dividing the Polynomials

To find [tex]\((f \div g)(x)\)[/tex], we divide [tex]\(f(x)\)[/tex] by [tex]\(g(x)\)[/tex]:

[tex]\[ f(x) = 15x^2 + 19x + 6 \][/tex]
[tex]\[ g(x) = 5x + 3 \][/tex]

Perform polynomial division:

We start by dividing the leading term of [tex]\(f(x)\)[/tex] by the leading term of [tex]\(g(x)\)[/tex]:

[tex]\[ \frac{15x^2}{5x} = 3x \][/tex]

Now, multiply [tex]\(g(x)\)[/tex] by [tex]\(3x\)[/tex] and subtract this product from [tex]\(f(x)\)[/tex]:

[tex]\[ (15x^2 + 19x + 6) - (3x \cdot (5x + 3)) \][/tex]
[tex]\[ (15x^2 + 19x + 6) - (15x^2 + 9x) \][/tex]
[tex]\[ (15x^2 + 19x + 6) - 15x^2 - 9x \][/tex]
[tex]\[ (15x^2 - 15x^2) + (19x - 9x) + 6 \][/tex]
[tex]\[ 10x + 6 \][/tex]

Next, divide [tex]\(10x\)[/tex] by [tex]\(5x\)[/tex]:

[tex]\[ \frac{10x}{5x} = 2 \][/tex]

Multiply [tex]\(g(x)\)[/tex] by [tex]\(2\)[/tex] and subtract from the remaining polynomial:

[tex]\[ (10x + 6) - (2 \cdot (5x + 3)) \][/tex]
[tex]\[ (10x + 6) - (10x + 6) \][/tex]
[tex]\[ 10x + 6 - 10x - 6 \][/tex]
[tex]\[ 0 \][/tex]

So, the quotient is:

[tex]\[ \boxed{3x + 2} \][/tex]

Putting everything together, we have:

[tex]\[ (f \cdot g)(x) = 75x^3 + 140x^2 + 87x + 18 \][/tex]
[tex]\[ (f \div g)(x) = 3x + 2 \][/tex]

Thus, the correct answers are:
[tex]\((f \cdot g)(x) = 75x^3 + 140x^2 + 87x + 18\)[/tex]
[tex]\((f \div g)(x) = 3x + 2\)[/tex]