Question 180326
9x^4=25x^2-16

9x^4 - 25x^2 + 16 = 0

Quadratic Formula:

x^2 = [25 +- sqrt(625 - 4*9*+16)]/18

x^2 = [25 +- sqrt(49)]/18

x^2 = [25 + 7]/18 or x^2 = [25 - 7]/18

x^2 = 16/9 or x^2 = 1

x = (4/3) or x = (-4/3) or x = 1 or x= -1
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Cheers
Stan H.