find the root of
![\sqrt{ {3x}^{2} } + \sqrt{6} = 9 \sqrt{ {3x}^{2} } + \sqrt{6} = 9](https://tex.z-dn.net/?f=+%5Csqrt%7B+%7B3x%7D%5E%7B2%7D+%7D+%2B+%5Csqrt%7B6%7D+%3D+9)
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= √3x² + √6 = 9
Squaring both sides
= (√3x² + √6 )² = 9²
= 3x² + 6 + 2√18x² - 81 = 0
= 3x² + 6x√2 - 75 = 0
= 3 ( x² + 2x√2 - 25 ) = 0
= x² + 2x√2 - 25 = 0
= Discriminant = 2√2² - 4*-25
= Discriminant = 8 + 100 = 108
= √Discriminant = √108 = 6√3
So roots = - b + √D / 2a, - b - √D / 2a
= 2√2 + 6√3 / 2 , 2√2 - 6√3 / 2
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