Solve (-x)² - 25: Working with Squared Negative Variables

Quadratic Equations with Perfect Square Patterns

(x)2(+25)= (-x)^2-(+25)=

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1

Understand the problem

(x)2(+25)= (-x)^2-(+25)=

2

Step-by-step solution

To solve this problem, we'll proceed as follows:

  • Step 1: Recognize that (x)2=x2(-x)^2 = x^2.
  • Step 2: Establish the equation by substituting: x225=0x^2 - 25 = 0.
  • Step 3: Recognize this as a difference of squares: (x5)(x+5)=0(x - 5)(x + 5) = 0.
  • Step 4: Solve for xx from the factors: x5=0x - 5 = 0 and x+5=0x + 5 = 0.
  • Step 5: Find solutions: x=5x = 5 and x=5x = -5.

Therefore, the solution to the equation is x=±5x = \pm 5.

The correct choice among the options provided is x=±5x = \pm 5.

3

Final Answer

x=±5 x=±5

Key Points to Remember

Essential concepts to master this topic
  • Rule: (x)2=x2(-x)^2 = x^2 because negative times negative equals positive
  • Technique: Factor difference of squares: x225=(x5)(x+5)=0x^2 - 25 = (x-5)(x+5) = 0
  • Check: Substitute both solutions: (5)225=0(-5)^2 - 25 = 0 and (5)225=0(5)^2 - 25 = 0

Common Mistakes

Avoid these frequent errors
  • Thinking (-x)² equals -x²
    Don't confuse (x)2(-x)^2 with x2-x^2 = wrong sign! The parentheses make all the difference: (x)2=(1x)2=(1)2x2=x2(-x)^2 = (-1 \cdot x)^2 = (-1)^2 \cdot x^2 = x^2. Always remember that squaring a negative gives positive.

Practice Quiz

Test your knowledge with interactive questions

Solve:

\( (2+x)(2-x)=0 \)

FAQ

Everything you need to know about this question

Why does (-x)² equal x² instead of -x²?

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The parentheses make all the difference! (x)2(-x)^2 means you're squaring the entire negative value, and negative times negative equals positive. So (x)2=x2(-x)^2 = x^2.

How do I know this is a difference of squares?

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Look for the pattern a2b2a^2 - b^2! Here we have x225=x252x^2 - 25 = x^2 - 5^2, which factors as (x5)(x+5)(x-5)(x+5). Both terms are perfect squares separated by subtraction.

Why are there two solutions instead of one?

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Because we're solving a quadratic equation! When we factor (x5)(x+5)=0(x-5)(x+5) = 0, either factor can equal zero. This gives us x=5x = 5 or x=5x = -5.

What if I forgot the difference of squares formula?

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You can still solve x2=25x^2 = 25 by taking the square root of both sides. Just remember: x2=x\sqrt{x^2} = |x|, so you get x=±5x = ±5.

How do I check my answer?

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Substitute both solutions back into the original equation. For x=5x = 5: (5)225=2525=0(-5)^2 - 25 = 25 - 25 = 0 ✓. For x=5x = -5: ((5))225=5225=0(-(−5))^2 - 25 = 5^2 - 25 = 0 ✓.

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