Solve the Quadratic Equations: x² + 9 = 0 and 2x² + 8 = 0 Compared

Quadratic Equations with No Real Solutions

Solve each equation separately and find which x is the largest.

  1. x2+9=0 x^2+9=0

  2. 2x2+8=0 2x^2+8=0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:10 Let's find the largest value of X.
00:13 First, we're going to work on section one. Let's solve for X here.
00:18 Our goal is to isolate X, step by step.
00:22 Remember, any number squared is always zero or more.
00:26 But, negative nine is less than zero. So, no solution for section one.
00:34 Now, let's move on to section two to find X.
00:38 Again, we'll isolate X to see what we can find.
00:46 Just like before, any number squared is zero or more.
00:52 Minus four is less than zero, so there's also no solution here.
00:58 And that's how we figure out this problem!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve each equation separately and find which x is the largest.

  1. x2+9=0 x^2+9=0

  2. 2x2+8=0 2x^2+8=0

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Solve the equation x2+9=0 x^2 + 9 = 0
  • Step 2: Solve the equation 2x2+8=0 2x^2 + 8 = 0
  • Step 3: Compare the solutions (if any) to identify the largest x x

Step 1: Solving x2+9=0 x^2 + 9 = 0 :
First, isolate x2 x^2 by subtracting 9 9 from both sides:
x2=9 x^2 = -9 .
Since x2=9 x^2 = -9 , trying to find the square root leads to x=±9 x = \pm \sqrt{-9} ,
which involves the imaginary unit i i , hence no real solution exists.

Step 2: Solving 2x2+8=0 2x^2 + 8 = 0 :
First, isolate 2x2 2x^2 by subtracting 8 8 from both sides:
2x2=8 2x^2 = -8 .
Divide each side by 2 2 :
x2=4 x^2 = -4 .
Attempting to take the square root results in x=±4 x = \pm \sqrt{-4} ,
which similarly involves the imaginary unit i i , so no real solution exists.

Step 3: Compare the solutions:
Since both equations yield no real solutions, there is no value of x x to compare.

Therefore, there is no solution to the two equations.

3

Final Answer

There is no solution to the two equations

Key Points to Remember

Essential concepts to master this topic
  • Rule: When x² equals a negative number, no real solutions exist
  • Technique: Isolate x² first: x² + 9 = 0 becomes x² = -9
  • Check: Square roots of negative numbers are imaginary, not real ✓

Common Mistakes

Avoid these frequent errors
  • Trying to find real square roots of negative numbers
    Don't write x = ±3 when x² = -9 = impossible real solution! Square roots of negative numbers don't exist in the real number system. Always recognize when x² equals a negative value means no real solutions exist.

Practice Quiz

Test your knowledge with interactive questions

Solve the following equation:


\( 2x^2-8=x^2+4 \)

FAQ

Everything you need to know about this question

Why can't I take the square root of a negative number?

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In the real number system, no real number multiplied by itself gives a negative result. For example, both 3×3=9 and (-3)×(-3)=9, never -9!

What does 'no real solutions' actually mean?

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It means there are no values of x that you can substitute back into the equation to make it true using real numbers. The solutions exist in the complex number system instead.

Are both equations really the same type of problem?

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Yes! Both x2+9=0 x^2 + 9 = 0 and 2x2+8=0 2x^2 + 8 = 0 simplify to x² = negative number, which means no real solutions for either.

How do I know when to look for 'no real solutions'?

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After isolating x², if you get x² = negative number, immediately conclude 'no real solutions' rather than trying to take square roots.

Could the answer be zero instead of 'no solutions'?

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No! Zero is a real number. When we say 'no real solutions,' we mean there are literally no real number values that work, not that the answer is zero.

What if I'm asked to compare solutions that don't exist?

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When both equations have no real solutions, there's nothing to compare! The correct answer is that comparison is impossible because no real solutions exist.

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