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The quadratic function [tex]\( f(x) \)[/tex] has roots of -2 and 3, and the point [tex]\( (2, -4) \)[/tex] lies on [tex]\( f(x) \)[/tex]. What is the equation of [tex]\( f(x) \)[/tex]?

A. [tex]\( f(x) = 2(x+2)(x-3) \)[/tex]
B. [tex]\( f(x) = 2(x-2)(x+3) \)[/tex]
C. [tex]\( f(x) = (x+2)(x-3) \)[/tex]
D. [tex]\( f(x) = (x-2)(x+3) \)[/tex]


Sagot :

To determine the equation of the quadratic function [tex]\( f(x) \)[/tex] with roots [tex]\(-2\)[/tex] and [tex]\(3\)[/tex] and which passes through the point [tex]\((2, -4)\)[/tex], follow these steps:

1. General Form: Given that the function has roots [tex]\(-2\)[/tex] and [tex]\(3\)[/tex], we can write it in its factorized form:
[tex]\[ f(x) = a(x + 2)(x - 3) \][/tex]
where [tex]\( a \)[/tex] is a constant that we need to determine.

2. Substitution of the Point:
We know that the point [tex]\((2, -4)\)[/tex] lies on [tex]\( f(x) \)[/tex]. This means when [tex]\( x = 2 \)[/tex], [tex]\( f(x) = -4 \)[/tex].
Substitute [tex]\( x = 2 \)[/tex] and [tex]\( f(x) = -4 \)[/tex] into the equation:
[tex]\[ -4 = a(2 + 2)(2 - 3) \][/tex]

3. Solve for [tex]\( a \)[/tex]:
Simplify the expression:
[tex]\[ -4 = a(4)(-1) \][/tex]
[tex]\[ -4 = -4a \][/tex]
Divide both sides by [tex]\(-4\)[/tex]:
[tex]\[ 1 = a \][/tex]

4. Formulate the Final Equation:
Now that we know [tex]\( a = 1 \)[/tex], we substitute [tex]\( a \)[/tex] back into the factorized form:
[tex]\[ f(x) = (x + 2)(x - 3) \][/tex]

5. Conclusion:
Comparing this result with the given options, we find that the correct function is:
[tex]\[ f(x) = (x + 2)(x - 3) \][/tex]
Therefore, the correct answer is:

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