High School

Select the correct answer.

Which of these is the standard form of the following function?

[tex] f(x) = -9(x+5)^2 + 4 [/tex]

A. [tex] f(x) = -9x^2 - 180x - 221 [/tex]

B. [tex] f(x) = 9x^2 - 90x - 221 [/tex]

C. [tex] f(x) = -9x^2 - 90x - 221 [/tex]

D. [tex] f(x) = 9x^2 - 180x + 221 [/tex]

Answer :

Sure! Let's find the standard form of the given function step-by-step.

We start with the function in its vertex form:

[tex]\[ f(x) = -9(x + 5)^2 + 4 \][/tex]

To convert this function into its standard form (which is of the form [tex]\( ax^2 + bx + c \)[/tex]), we need to expand the expression.

1. First, let's expand the squared term [tex]\((x + 5)^2\)[/tex]:

[tex]\[ (x + 5)^2 = x^2 + 10x + 25 \][/tex]

2. Now, substitute this expansion back into the original function:

[tex]\[ f(x) = -9(x^2 + 10x + 25) + 4 \][/tex]

3. Next, distribute the [tex]\(-9\)[/tex] over each term inside the parentheses:

[tex]\[ f(x) = -9x^2 - 90x - 225 + 4 \][/tex]

4. Finally, combine the constant terms [tex]\(-225\)[/tex] and [tex]\(4\)[/tex]:

[tex]\[ f(x) = -9x^2 - 90x - 221 \][/tex]

Thus, the standard form of the given function is:

[tex]\[ f(x) = -9x^2 - 90x - 221 \][/tex]

So, the correct answer is:

[tex]\[ \boxed{f(x) = -9x^2 - 90x - 221} \][/tex]