High School

Which of the following expressions is equivalent to [tex]-4x^3 - 12x^3 + 9x^2[/tex]?

A. [tex]x^8[/tex]

B. [tex]-7x^8[/tex]

C. [tex]-8x^3 + 9x^2[/tex]

D. [tex]-16x^3 + 9x^2[/tex]

E. [tex]-16x^6 + 9x^2[/tex]

Answer :

To solve the expression and find which of the given choices is equivalent to [tex]\(-4x^3 - 12x^3 + 9x^2\)[/tex], let's simplify it step-by-step:

1. Identify Like Terms:
- The terms [tex]\(-4x^3\)[/tex] and [tex]\(-12x^3\)[/tex] are like terms because they both have [tex]\(x^3\)[/tex].
- The term [tex]\(9x^2\)[/tex] is separate and independent as it involves [tex]\(x^2\)[/tex] rather than [tex]\(x^3\)[/tex].

2. Combine Like Terms:
- For the [tex]\(x^3\)[/tex] terms:
[tex]\[
-4x^3 - 12x^3 = (-4 - 12)x^3 = -16x^3
\][/tex]
- The [tex]\(x^2\)[/tex] term remains as [tex]\(9x^2\)[/tex].

3. Write the Simplified Expression:
- After combining the like terms, the simplified expression is:
[tex]\[
-16x^3 + 9x^2
\][/tex]

Now, compare this simplified expression to the choices provided:

- [tex]\(x^8\)[/tex]
- [tex]\(-7x^8\)[/tex]
- [tex]\(-8x^3 + 9x^2\)[/tex]
- [tex]\(-16x^3 + 9x^2\)[/tex]
- [tex]\(-16x^6 + 9x^2\)[/tex]

The equivalent expression is [tex]\(-16x^3 + 9x^2\)[/tex], which matches the choice:

[tex]\(-16x^3 + 9x^2\)[/tex].

So, the expression equivalent to [tex]\(-4x^3 - 12x^3 + 9x^2\)[/tex] is [tex]\(\boxed{-16x^3 + 9x^2}\)[/tex].