Checking Solutions Math Example 2

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Example 2

medium
Solve x+3=xโˆ’3\sqrt{x+3} = x - 3 and check for extraneous solutions.

Solution

  1. 1
    Square both sides: x+3=(xโˆ’3)2=x2โˆ’6x+9x + 3 = (x-3)^2 = x^2 - 6x + 9.
  2. 2
    Rearrange: x2โˆ’7x+6=0x^2 - 7x + 6 = 0, factor: (xโˆ’1)(xโˆ’6)=0(x-1)(x-6) = 0.
  3. 3
    Candidates: x=1x = 1 and x=6x = 6.
  4. 4
    Check x=1x = 1: 4=2\sqrt{4} = 2 but 1โˆ’3=โˆ’21 - 3 = -2. 2โ‰ โˆ’22 \neq -2 โœ— (extraneous).
  5. 5
    Check x=6x = 6: 9=3\sqrt{9} = 3 and 6โˆ’3=36 - 3 = 3. 3=33 = 3 โœ“

Answer

x=6x = 6 only (x=1x = 1 is extraneous).
Squaring both sides can introduce false solutions. Always check candidates in the original equation to catch extraneous solutions.

About Checking Solutions

Checking solutions means substituting candidate values back into the original condition to verify they satisfy it.

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