Convert the Quadratic Expression (-x-2)² - 5 to Its Standard Form

Quadratic Expansion with Perfect Square Binomials

Find the standard representation of the following function

f(x)=(x2)25 f(x)=(-x-2)^2-5

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00:00 Simplified to the standard representation of the function
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Step-by-step written solution

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1

Understand the problem

Find the standard representation of the following function

f(x)=(x2)25 f(x)=(-x-2)^2-5

2

Step-by-step solution

To find the standard representation of the quadratic function f(x)=(x2)25 f(x)=(-x-2)^2-5 , we'll proceed with the following steps:

  • Step 1: Expand the quadratic expression (x2)2(-x-2)^2.
  • Step 2: Simplify the expression resulting from the expansion.
  • Step 3: Subtract the constant term 5-5.

Let's execute these steps in detail:

Step 1: Expand the expression (x2)2(-x-2)^2.
To expand, use the formula (a+b)2=a2+2ab+b2(a+b)^2 = a^2 + 2ab + b^2, where a=xa=-x and b=2b=-2.
(x2)2=(x)2+2(x)(2)+(2)2(-x-2)^2 = (-x)^2 + 2(-x)(-2) + (-2)^2.

Step 2: Calculate the expanded form.
(x)2=x2(-x)^2 = x^2,
2(x)(2)=4x2(-x)(-2) = 4x,
and (2)2=4(-2)^2 = 4.
Combining these, we have:
x2+4x+4x^2 + 4x + 4.

Step 3: Incorporate the constant from the original function.
The original function is f(x)=(x2)25f(x)=(-x-2)^2-5. Thus, we subtract 5 from the expanded result:
f(x)=x2+4x+45f(x) = x^2 + 4x + 4 - 5, which simplifies to:
f(x)=x2+4x1f(x) = x^2 + 4x - 1.

Therefore, the standard form of the given quadratic function is f(x)=x2+4x1 f(x) = x^2 + 4x -1 .

3

Final Answer

f(x)=x2+4x1 f(x)=x^2+4x-1

Key Points to Remember

Essential concepts to master this topic
  • Rule: Use (a+b)² = a² + 2ab + b² for perfect square expansion
  • Technique: For (-x-2)², identify a = -x and b = -2, then expand systematically
  • Check: Substitute x = 0: (-0-2)² - 5 = 4 - 5 = -1 matches x² + 4x - 1 ✓

Common Mistakes

Avoid these frequent errors
  • Incorrectly handling negative signs during expansion
    Don't forget that (-x)² = x², not -x²! Many students write (-x)² as -x² which gives the wrong answer entirely. Always remember that squaring a negative expression makes it positive, so (-x)² always equals x².

Practice Quiz

Test your knowledge with interactive questions

Create an algebraic expression based on the following parameters:

\( a=2,b=2,c=2 \)

FAQ

Everything you need to know about this question

Why does (-x)² equal x² and not -x²?

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Because squaring always makes things positive! When you square (-x), you're multiplying (-x) × (-x), and negative times negative equals positive. So (-x)² = x².

How do I remember the perfect square formula?

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Think "First squared, plus twice the product, plus last squared". For (a+b)²: (first squared) + 2ab (twice the product) + (last squared).

What if I have (-x-2)² instead of (-x+2)²?

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No problem! Just treat it as (x)+(2)(-x) + (-2)². So a = -x and b = -2. The formula still works: (-x)² + 2(-x)(-2) + (-2)².

How can I check if my expansion is correct?

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Pick any simple value for x (like x = 1) and substitute it into both the original expression and your expanded form. If they give the same result, you're correct!

Do I always need to expand quadratics to standard form?

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Not always! But standard form ax2+bx+cax² + bx + c is most useful for graphing, finding roots with the quadratic formula, and identifying key features like the y-intercept.

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