Solving Radical Equations
Equations containing radicals
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Solving Radical Equations
Strategy
- Isolate the radical on one side
- Raise both sides to the appropriate power
- Solve the resulting equation
- Check for extraneous solutions
Why Check?
Squaring both sides can introduce extraneous solutions.
Always substitute back into the original equation!
Multiple Radicals
If there are two radicals:
- Isolate one radical
- Square both sides
- Isolate the remaining radical
- Square again
- Solve and check
Domain Restrictions
For : must have
For : can be any real number
Example
Solve:
Square both sides:
Check: ✓
📚 Practice Problems
1Problem 1easy
❓ Question:
Solve: √x = 5
💡 Show Solution
Step 1: Square both sides: (√x)² = 5² x = 25
Step 2: Check the solution: √25 = 5 ✓
Answer: x = 25
2Problem 2easy
❓ Question:
Solve:
💡 Show Solution
Square both sides:
Solve for :
Check: ✓
Answer:
3Problem 3easy
❓ Question:
Solve: √(x + 3) = 4
💡 Show Solution
Step 1: Square both sides: (√(x + 3))² = 4² x + 3 = 16
Step 2: Solve for x: x = 16 - 3 x = 13
Step 3: Check the solution: √(13 + 3) = √16 = 4 ✓
Answer: x = 13
4Problem 4medium
❓ Question:
Solve:
💡 Show Solution
Step 1: Isolate the radical
Step 2: Square both sides
Step 3: Solve
Check: ✓
Answer:
5Problem 5medium
❓ Question:
Solve: √(2x - 1) = x - 2
💡 Show Solution
Step 1: Square both sides: (√(2x - 1))² = (x - 2)² 2x - 1 = x² - 4x + 4
Step 2: Rearrange to standard form: 0 = x² - 4x - 2x + 4 + 1 0 = x² - 6x + 5
Step 3: Factor: 0 = (x - 5)(x - 1)
Step 4: Solve: x = 5 or x = 1
Step 5: Check x = 5: √(2(5) - 1) = √9 = 3 5 - 2 = 3 ✓
Step 6: Check x = 1: √(2(1) - 1) = √1 = 1 1 - 2 = -1 ✗ x = 1 is EXTRANEOUS
Answer: x = 5
6Problem 6medium
❓ Question:
Solve: √(x + 7) - √(x - 5) = 2
💡 Show Solution
Step 1: Isolate one radical: √(x + 7) = 2 + √(x - 5)
Step 2: Square both sides: x + 7 = (2 + √(x - 5))² x + 7 = 4 + 4√(x - 5) + (x - 5) x + 7 = x - 1 + 4√(x - 5)
Step 3: Simplify: x + 7 - x + 1 = 4√(x - 5) 8 = 4√(x - 5) 2 = √(x - 5)
Step 4: Square again: 4 = x - 5 x = 9
Step 5: Check x = 9: √(9 + 7) - √(9 - 5) = √16 - √4 = 4 - 2 = 2 ✓
Answer: x = 9
7Problem 7hard
❓ Question:
Solve:
💡 Show Solution
Step 1: Square both sides
Step 2: Rearrange to standard form
Step 3: Factor
Step 4: Solve
Step 5: Check both solutions
For : and ✓
For : and ✗
Answer: only (x = 2 is extraneous)
8Problem 8hard
❓ Question:
Solve: ∛(x + 1) = 2
💡 Show Solution
Step 1: Cube both sides: (∛(x + 1))³ = 2³ x + 1 = 8
Step 2: Solve for x: x = 7
Step 3: Check: ∛(7 + 1) = ∛8 = 2 ✓
Step 4: Note about odd roots: Unlike even roots, odd roots can have negative radicands For example, ∛(-8) = -2
Answer: x = 7
⚠️ Common Mistakes: Solving Radical Equations
Avoid these 3 frequent errors
🌍 Real-World Applications: Solving Radical Equations
See how this math is used in the real world
📝 Worked Example: Solving a Quadratic by Factoring
Solve .
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