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The expansion of (9 – 4x^2)^(1/2) – Algebra

The expansion of \({(9\;-\;4x^2)}^\frac12\) is valid for
  1. \(-\frac12\leq x\;\leq1\)
  2. \(-2\leq x\;\leq\frac12\)
  3. \(-\frac13\leq x\;\leq\frac13\)
  4. \(-\frac32\leq x\;\leq\frac32\)

2 Answers


\({(9\;-\;4x^2)}^\frac12\)

= \(3\left(1-\frac{4x^2}9\right)^\frac12\)

This is valid if \(\frac{4x^2}9<1\)

Or, \(x^2<\frac94\;or,\;\left|x\right|<\frac32\;\)

∴ \(-\frac32\leq x\;\leq\frac32\)

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