Question 177410
15x^4-28x^2+5=0
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15x^4 - 25x^2 - 3x^2 + 5 = 0

5x^2(3x^2 - 5) - (3x^2 - 5) = 0

(3x^2 - 5)(5x^2 - 1) = 0
x^2 = 5/3 or x^2 = 1/5
x = +/-sqrt(5/3) or x = +/-sqrt(1/5)

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Cheers,
Stan H.