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How Do You Use the Square Root Method to Solve a Quadratic Equation with Imaginary Solutions?
Solve the quadratic equation x2 + 38 = 2 for x.
Summary
- Subtract 38 from both sides to isolate x2
- The symbol above the x2 and -36 is the square root symbol
- '
± ' means 'plus or minus' - We have a '
± ' to account for both the positive and negative square roots of -36 - Factoring out the -1 from -36 will allow us to deal with just the positive part of the square root
- The Product Property of Square Roots splits the square root into the product of two square roots
- 'i' is the imaginary unit and is equal to the square root of -1

Notes
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- There are multiple methods to solve a quadratic equation
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- There are multiple methods to solve a quadratic equation
- Since there is no 'x' term, we can use the square root method
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- The first step in solving for 'x' is to get x2 by itself
- The Subtraction Property of Equality allows us to subtract 38 from both sides
- On the right we have 2-38 = -36
- On the left we have x2+38-38 = x2
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- Taking the square root of both sides will get rid of the square on the x2
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- Squaring the negative version of a number gives you the same result as squaring the positive version
- For example, squaring 6 and -6 will both give you 36
- So the square root of 36 could be either positive or negative
- Check out the Square Root Property to learn more
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- We still have a perfect square term under the square root symbol, so we can simplify this further!
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We can rewrite
√ (-1•36) as two radicals multiplied together: -
The square root of -1 and the square root of 36, or
√ (-1)•√ (36)
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We can rewrite
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- 'i' is the imaginary unit and is equal to the square root of -1
- 'i' is NOT a variable!
- The symbol above the -1 and 36 is the square root symbol
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'
± ' means 'plus or minus' - The square root of 36 is just 6
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'
± ' means 'plus or minus' - So 'plus or minus 6i' means that we have two possible answers: positive 6i or negative 6i
- 'i' is the imaginary unit and is equal to the square root of -1
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'