Math Problem Statement

f(x) = −x^2 − 4x + 2 write in standard form

Solution

To rewrite the given quadratic function f(x)=x24x+2f(x) = -x^2 - 4x + 2 in standard form, we need to express it as:

f(x)=a(xh)2+kf(x) = a(x - h)^2 + k

where aa, hh, and kk are constants, and (h,k)(h, k) represents the vertex of the parabola.

Step-by-step process:

  1. Factor out the coefficient of the quadratic term (if necessary): In this case, the coefficient of x2x^2 is already 1-1, so we proceed without factoring for now.

    f(x)=(x2+4x)+2f(x) = - (x^2 + 4x) + 2

  2. Complete the square: To complete the square inside the parentheses, take half of the coefficient of xx (which is 44), square it, and add/subtract it inside the equation.

    Half of 44 is 22, and 22=42^2 = 4. So, we add and subtract 44 inside the parentheses:

    f(x)=(x2+4x+44)+2f(x) = - (x^2 + 4x + 4 - 4) + 2

    Simplifying this gives:

    f(x)=[(x+2)24]+2f(x) = - \left[(x + 2)^2 - 4\right] + 2

  3. Simplify the expression: Distribute the negative sign and simplify:

    f(x)=(x+2)2+4+2f(x) = - (x + 2)^2 + 4 + 2

    f(x)=(x+2)2+6f(x) = - (x + 2)^2 + 6

Final standard form:

f(x)=(x+2)2+6f(x) = - (x + 2)^2 + 6

This is the standard form of the quadratic function. Here:

  • a=1a = -1
  • h=2h = -2
  • k=6k = 6

The vertex of the parabola is at (2,6)(-2, 6).

Would you like further details or have any questions?


Here are 5 questions to expand on this concept:

  1. How do you find the vertex of a parabola given the standard form?
  2. What does the sign of the coefficient aa tell us about the graph of a quadratic function?
  3. How does completing the square help in graphing quadratic functions?
  4. Can we convert a quadratic function in standard form back to its general form?
  5. How do transformations of f(x)=x2f(x) = x^2 relate to changes in the quadratic function?

Tip: Completing the square is a useful technique not only for rewriting quadratics but also for solving quadratic equations!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Functions
Completing the Square

Formulas

Standard form of a quadratic function: f(x) = a(x - h)^2 + k
Completing the square process

Theorems

Vertex form of a quadratic function

Suitable Grade Level

Grades 9-11