College

Factor the trinomial completely:

[tex]2x^4 - 24x^2 + 70[/tex]

Select the correct choice below:

A. [tex]2x^4 - 24x^2 + 70 = \square[/tex]

B. The polynomial is prime.

Answer :

We start with the polynomial

[tex]$$
2x^4 - 24x^2 + 70.
$$[/tex]

Step 1. Factor out the greatest common factor

Notice that all terms are even, so we can factor out a [tex]$2$[/tex]:

[tex]$$
2x^4 - 24x^2 + 70 = 2\left(x^4 - 12x^2 + 35\right).
$$[/tex]

Step 2. Recognize the quadratic form in [tex]$x^2$[/tex]

The expression inside the parentheses, [tex]$x^4 - 12x^2 + 35$[/tex], is a quadratic in [tex]$x^2$[/tex]. To see this clearly, let

[tex]$$
y = x^2.
$$[/tex]

Then

[tex]$$
x^4 - 12x^2 + 35 = y^2 - 12y + 35.
$$[/tex]

Step 3. Factor the quadratic

We now factor the quadratic

[tex]$$
y^2 - 12y + 35.
$$[/tex]

We are looking for two numbers that multiply to [tex]$35$[/tex] and add to [tex]$-12$[/tex]. These numbers are [tex]$-5$[/tex] and [tex]$-7$[/tex], because

[tex]$$
(-5)(-7) = 35 \quad \text{and} \quad (-5) + (-7) = -12.
$$[/tex]

Thus, the quadratic factors as

[tex]$$
y^2 - 12y + 35 = (y - 5)(y - 7).
$$[/tex]

Step 4. Substitute back [tex]$x^2$[/tex] for [tex]$y$[/tex]

Replacing [tex]$y$[/tex] by [tex]$x^2$[/tex], we obtain

[tex]$$
x^4 - 12x^2 + 35 = (x^2 - 5)(x^2 - 7).
$$[/tex]

Step 5. Write the final factorization

Substituting this back into our original expression, we have

[tex]$$
2x^4 - 24x^2 + 70 = 2(x^2 - 5)(x^2 - 7).
$$[/tex]

Thus, the complete factorization of the trinomial is:

[tex]$$
\boxed{2(x^2 - 5)(x^2 - 7)}.
$$[/tex]