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How to solve square root equations?

User Teun
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Example: solve √(2x−5) − √(x−1) = 1isolate one of the square roots: √(2x−5) = 1 + √(x−1)square both sides: 2x−5 = (1 + √(x−1))2We have removed one square root.Expand right hand side: 2x−5 = 1 + 2√(x−1) + (x−1)Simplify: 2x−5 = 2√(x−1) + xSubtract x from both sides: x−5 = 2√(x−1) Now do the "square root" thing again:isolate the square root: √(x−1) = (x−5)/2square both sides: x−1 = ((x−5)/2)2We have now successfully removed both square roots. Let us continue on with the solution.Expand right hand side: x−1 = (x2 − 10x + 25)/4It is a Quadratic Equation! So let us put it in standard form.Multiply by 4 to remove division: 4x−4 = x2 − 10x + 25Bring all to left: 4x − 4 − x2 + 10x − 25 = 0Combine like terms: −x2 + 14x − 29 = 0Swap all signs: x2 − 14x + 29 = 0Using the Quadratic Formula (a=1, b=−14, c=29) gives the solutions:2.53 and 11.47 (to 2 decimal places)Let us check the solutions:2.53: √(2·2.53−5) − √(2.53−1) ≈ −1 Oops! Should be plus 1! 11.47: √(2·11.47−5) − √(11.47−1) ≈ 1 Yes that one works. There is really only one solution: Answer: 11.47 (to 2 decimal places)
User Abarax
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